2002: Pro debut Sitak began his senior career in 2002 at a challenger event in Togliatti, Russia, where he received a wildcard into the main draw but fell in the first round to
Thomas Blake, older brother of former top 10 player
James Blake.
2005: First Futures title Sitak's first title came in 2005 in a Russian Futures tournament, where he defeated
Pavel Chekhov 4–6, 6–4, 6–4 in the final.
2011 Sitak began 2011 under the New Zealand flag and received a wildcard into the
2011 Heineken Open qualifying, where he was defeated by Frenchman
Ludovic Walter 6–3, 6–4 in the first round.
2012 He won the men's singles in the
Ojai Tennis Tournament in 2012.
2014: First ATP doubles title Sitak partnered Polish tennis player
Mateusz Kowalczyk to win the
2014 MercedesCup doubles title, defeating
Philipp Oswald and
Guillermo García López 2–6, 6–1, 10–7 in the final.
2017: New partnership with Koolhof Sitak's long-running doubles partnership with
Nicholas Monroe came to an end after
Wimbledon in 2017, and he subsequently teamed up with Dutch player
Wesley Koolhof. They reached the final in Atlanta, losing to the Bryan brothers, and lost in the first round at the
US Open before winning a Challenger event in Szczecin, Poland, and losing another ATP final, this time in Metz, to
Julien Benneteau and
Édouard Roger-Vasselin.
2018 Starting the new year in
Brisbane, Sitak and Koolhof lost in the semi-finals to
Leonardo Mayer and
Horacio Zeballos. They lost in the first round in
Auckland to
Michael Venus and
Raven Klaasen, and then 7–6(5), 4–6, 4–6 in the second round of the
Australian Open to the eventual winners,
Oliver Marach and
Mate Pavić. Although they were not in the original draw for the Mixed Doubles, Sitak and
Olga Savchuk teamed up as alternates after an injury to
Anastasia Rodionova in her women's doubles match meant that she and Marach could not participate. They were beaten in a first-round match tie-break by
Nadiia Kichenok and
Marcel Granollers. Sitak and Koolhof then went to Newport Beach in California where, as top seeds, they lost in the first round, 2–6, 1–6, to
Treat Huey and
Denis Kudla. After that came the
Davis Cup where, in
Tianjin, Sitak and
Marcus Daniell lost their doubles tie to the lowly-ranked Chinese pair of
Gong Mao-Xin and
Zhang Ze. Sitak and Koolhof then lost in the quarter-finals at
Montpellier before going all the way to the final in the
New York Open, being beaten by
Max Mirnyi and
Philipp Oswald in a match tie-break. They followed that up with a first round loss at
Delray Beach to
Scott Lipsky and
Divij Sharan. Their up and down season continued in Brazil, where they reached the final in
São Paulo, but were beaten in straight sets by
Federico Delbonis and
Máximo González. Their next stop was Irving, Texas, where they lost in the semi-finals of the
ATP Challenger to
Alexander Peya and
Philipp Petzschner. Moving to Europe, and playing in the
Alicante Challenger in Spain as preparation for the European clay court season, they won their second title together when they beat
Guido Andreozzi and
Ariel Behar 6–3, 6–2, in the final, but they lost in the first round of their next tournament in
Marrakech. In the
Hungarian Open they beat the top seeds
Nikola Mektić and
Alexander Peya in the first round, but lost in the second to
Marcin Matkowski and Sitak's former partner
Nicholas Monroe. Their next tournament was at
Estoril where they went all the way to the final before losing to the British pair of
Kyle Edmund and
Cameron Norrie, 2–6, 4–6. They then lost in the first round of the
Bordeaux Challenger tournament after Sitak had been hit in the right ear by a smash from
Radu Albot, and also in the first round in
Geneva, the last tournament before the French Open. At
Roland Garros, Sitak and Koolhof beat
Andre Begemann and
Antonio Šančić in the first round, then the ninth seeds
Ivan Dodig and
Rajeev Ram, before going down to fifth seeds
Juan Sebastián Cabal and
Robert Farah. All three matches went to a deciding set. After the tournament finished it was announced that the pair would split, with Koolhof joining Sitak's fellow New Zealander, and former partner,
Marcus Daniell, and Sitak linking up with Indian
Divij Sharan. Sitak and Sharan's first tournament together was at
's-Hertogenbosch, where they were beaten in the semi-finals by
Michael Venus and
Raven Klaasen. They then lost in a big upset in the first round of qualifying at
Halle, before finding top seeds
Cabal and
Farah their nemesis in the first round at
Eastbourne. They reached the quarter-finals at
Wimbledon, the best-ever result in a Grand Slam tournament for either of them. They had to come from two sets down in both their second and third round matches, against
Julio Peralta and
Horacio Zeballos and
Marcin Matkowski and
Jonathan Erlich respectively, before lining up against
Mike Bryan and
Jack Sock in the quarter-finals. There were three tie-break sets to start, and just one loss of serve in the fourth set was enough to seal their defeat at the hands of the eventual champions. In mixed doubles, Sitak teamed up with Ukrainian
Lyudmyla Kichenok to beat Argentina's
Leonardo Mayer and
María Irigoyen, but he withdrew from the second round due to fatigue from the length of the men's doubles matches. Sitak teamed up with Erlich for the
Hall of Fame Championships in
Newport, marching imperiously to the final, where they very quickly swept aside clay-court specialists
Marcelo Arévalo and
Miguel Ángel Reyes-Varela. Sitak maintained that it was their experience which counted – it was the 39th ATP final for Erlich, and the 11th for Sitak, but just the first for both their opponents. Moving on to Washington, D.C. for the
Citi Open, Sitak and Sharan beat
Jamie Cerretani and
Leander Paes in the first round before losing to
Jamie Murray and
Bruno Soares in the quarter-finals. Sitak then entered the
Toronto Masters with
Stefanos Tsitsipas, and received a first-round call up as an alternate for a withdrawn pair. They ended up playing
Michael Venus and
Raven Klaasen, and lost 6–4, 6–4. Moving on to
Cincinnati for the next Masters event, the pair qualified for direct acceptance. In the first round they were drawn against
Ivan Dodig and
Robin Haase, and lost in a match tie-break. In his last tournament before the US Open, Sitak teamed up with
Aisam-ul-Haq Qureshi at
Winston-Salem. They beat
Max Mirnyi and
Philipp Oswald, then
Marcelo Demoliner and
Santiago González, before falling to
Jamie Cerretani and
Leander Paes in the semi-final. In the
US Open, Sitak and Sharan lost to eventual runners-up
Łukasz Kubot and
Marcelo Melo in the second round, while Sitak and
Lyudmyla Kichenok were beaten in a tight first round battle in the
mixed doubles, losing 10–8 in the match tie-break to fourth seeds
Latisha Chan and
Ivan Dodig. The US Open was followed by New Zealand's
Davis Cup tie against Korea in
Gimcheon, where Sitak and debutant
Ajeet Rai were successful in their doubles rubber. However, New Zealand lost the tie 3–2, and were relegated to Group II of the Asia/Oceania zone for the first time in five years. Dashing back to France for what turned out to be just one match, Sitak, again with Qureshi, lost in the first round at
Metz to
Oliver Marach and
Jürgen Melzer. Reunited with Sharan a week later in China, they were upset in the first round of the
Chengdu Open by
Austin Krajicek and
Jeevan Nedunchezhiyan. In the Japan Open they drew
Jamie Murray and
Bruno Soares in the first round, and lost in straight sets, and then were able to get into the
Shanghai Masters as an alternate entry, where they lost in the second round to Kubot and Melo, who went on to win the title. Their next event was the
European Open in Antwerp where, as fourth seeds, they lost to second seeds
Nicolas Mahut and
Édouard Roger-Vasselin in an entertaining semi-final. From there they travelled to
Basel for the
Swiss Indoors Open, where they lost in an upset result in the semi-finals to
Mischa and
Alexander Zverev. They finished their season at the
Paris Masters where, with only an hour's notice, they again took the court as an alternate. They beat
Feliciano and
Marc López in the first round, but lost in straight sets in the second round to the best team in the world for 2018,
Mike Bryan and
Jack Sock.
2019 With a new partner in the left-handed American
Austin Krajicek, Sitak began 2019 in
Brisbane, where they lost in the quarter-finals to
Rajeev Ram and
Joe Salisbury. They also lost in the quarter-finals in
Auckland, this time to
Bob and
Mike Bryan, the former playing his first tournament since being injured in Monte Carlo and subsequently having surgery to replace his hip. The
Australian Open also saw them record a win and a loss, beating
Leander Paes and
Miguel Ángel Reyes-Varela in the first round, but losing a tight match to eventual semi-finalists
Ryan Harrison and
Sam Querrey in the second, 6–4, 7–6(5). Sitak had another new partner in the mixed doubles, teaming up with former World doubles number one
Ekaterina Makarova. Seeded eighth, they lost in the first round to
Andreja Klepač and
Édouard Roger-Vasselin. Sitak and Krajicek then lost in the first round at
Montpellier before going to
Rotterdam, where they got into the main draw as Lucky Losers, but again lost in the first round. The same fate awaited them in
Rio de Janeiro, but they had far better luck in
Acapulco, where they finished runners-up to
Mischa and
Alexander Zverev after easily taking the first set of the final. It was the first ATP500 series final for both Sitak and Krajicek. Because of their relative rankings, Sitak found a new partner for
Indian Wells in singles specialist
Nikoloz Basilashvili, but they went out in the first round to eighth seeds
Henri Kontinen and
John Peers. That meant that he and Krajicek were able to go straight to
Phoenix, where they had walk-overs in the first two rounds of the
Phoenix Challenger, beat
Jamie Cerretani and
Nicholas Monroe in the semi-finals, and lost to
Jamie Murray and
Neal Skupski in the final. From there they went to
Miami, where they lost in the first round, and on to
Houston for the
US Clay Court Championships, where they lost to the Skupski brothers in the semi-finals. That was followed by a loss in qualifying in
Barcelona and a quarter-final loss in
Munich before a first round loss in
Madrid, where they had got in as an alternate pair. They also got into the
Italian Open as an alternate pair, and this time made it to the second round, losing to eventual champions
Juan Sebastián Cabal and
Robert Farah. Another first round loss, this time as second seeds in
Geneva, preceded their attempt at the
French Open, where Krajicek dropped a bombshell just a couple of days before their first round match by announcing that he would be ending their partnership after this tournament. Seeded 16th, the pair didn't have a single practice together before losing in the first round to
Hsieh Cheng-peng and
Christopher Rungkat. He and
Makoto Ninomiya played
mixed doubles together, but lost in a first round match tie-break to eventual semi-finalists
Nadiia Kichenok and
Aisam-ul-Haq Qureshi. Sitak had different partners for each of his first three grass tournaments before winning the
Antalya Open with
Jonathan Erlich in a week where the on-court temperatures seldom dropped below 40 degrees Celsius. They defeated
Ivan Dodig and
Filip Polášek in straight sets in the final, having beaten French Open champions
Kevin Krawietz and
Andreas Mies in the first round. At
Wimbledon Sitak and Erlich lost in the first round to
Máximo González and
Horacio Zeballos, but Sitak went much further in the
mixed doubles. Although he and
Laura Siegemund made it to the quarter-finals before losing to fifth seeds
Květa Peschke and
Wesley Koolhof, it's their first round match against
Darija Jurak and
Ken Skupski which will go down in history, the sprinklers facing Sitak and Siegemund bursting into life as they sat down with the score at 4–3 in the final set. The match was eventually moved to another court to be finished. As if that wasn't enough, their top quality third round match against third seeds
Gabriela Dabrowski and
Mate Pavić took three hours and 17 minutes, becoming the first mixed doubles match to require Wimbledon's innovation of a tie-break at 12–12 in the final set. Sitak and Erlich were unable to defend their title in
Newport, losing in the first round, before Sitak teamed up with
Radu Albot to reach the semi-finals in
Atlanta, but they lost in the first round in
Los Cabos. Next up was the
US Open, where Sitak and
Denys Molchanov lost in the first round to second seeds
Łukasz Kubot and
Marcelo Melo. The same fate befell him in the
mixed doubles, where he and
Lucie Hradecká also lost in the first round. Two more first round losses followed before Sitak reunited with
Divij Sharan. Although losing their first match together, they reached the quarter-finals of the
Japan Open. They made the
Paris Masters as alternates, beating Pavić and
Bruno Soares in the first round before losing to
Jérémy Chardy and
Fabrice Martin in the second. Two first round losses in Challenger events ended the 2019 season for Sitak.
2020 Sitak had a six-week break before he and Sharan started the new year with a first round loss in
Doha. They were more successful in
Auckland, upsetting top seeds
John Peers and
Michael Venus in the first round before losing a tight match in the second against
Sander Gillé and
Joran Vliegen. They lost in the second round of the
Australian Open to
Mate Pavić and
Bruno Soares and in the first round in
Pune when seeded second. Then followed three tournaments with a win and a loss –
New York,
Delray Beach (where they lost to eventual champions
Bob and
Mike Bryan) and the Chilean capital,
Santiago. The following week saw the pair split up to play for their respective countries in the
Davis Cup, with Sitak joining
Marcus Daniell for the first time in two years as
New Zealand played
Venezuela for the first time ever, in
Auckland. It was a successful return, as the pair won their rubber in straight sets to help New Zealand to a 3–1 win and a place in the next round, against
South Korea. Just a day later came the news that the partnership with Sharan was over, the Indian deciding that their results weren't good enough to justify continuing as a pair. That was followed by the suspension of all international tennis due to the COVID-19 coronavirus. Sitak returned to action in August with a new partner, Slovak
Igor Zelenay. They lost in the first round in two Challenger events in
Prague, but took their first title at the third attempt, in
Ostrava. They were the only alternate team to get into the
French Open, but lost in the first round, as they did in a Challenger in
Parma. They fared better at a new ATP250 tournament in
Santa Margherita di Pula, Sardinia, losing in the quarter-finals to eventual winners Marcus Daniell and
Philipp Oswald, but this was their last tournament together. With partners for just one tournament at a time, Sitak lost in the quarter-finals in
Istanbul and
Nur-Sultan, and in the first round of the
Paris Masters. He got to the quarter-finals of the
Sofia Open in Bulgaria before flying to South America for a final Challenger event, reaching the semi-finals in
Lima.
2021 The early part of 2021 saw Sitak continue to criss-cross the globe. Starting in Australia, Sitak and
Federico Delbonis lost in the second round of the
Great Ocean Road Open to fellow New Zealanders
Marcus Daniell and
Michael Venus, before Sitak and
Jonny O'Mara were eliminated in the first round of the
Australian Open by eventual runners-up
Rajeev Ram and
Joe Salisbury. Sitak then paired up with
Nicholas Monroe for the first time in several years, losing in the first round in three tournaments in South America before he moved north to
Acapulco. Although he and
Dominik Koepfer lost in the final qualifying round, they took their place in the main draw as Lucky Losers, but were beaten in a match tie-break by
Marcelo Demoliner and
Santiago González. Sitak then headed to Europe, where he and
Sergio Martos Gornés lost in the semi-finals of a Challenger event in
Lugano, having won a marathon match-tie break (17–15) in their previous match. That was followed by first round losses in both a
Challenger and an
ATP tournament in Marbella. At the
2021 Astana Open he reached the semifinal in doubles partnering
Ričardas Berankis, where they lost to top seeds and eventual champions
Santiago González and
Andrés Molteni.
2024: Retirement In January 2024, Sitak announced that he would retire from professional tennis. He played his final professional match at the
2024 ASB Classic. ==ATP career finals==