Early career, 2000–2005 Marco Chiudinelli played his first professional matches in 2000, but did not compete on a regular basis until 2002. That year he won his first tournament on the third-tier
Futures circuit in
Dubai, defeating a 16-year-old
Jimmy Wang in the final. He finished as runner-up to
Grégory Carraz at a Futures event in
Poitiers in March and secured a second Futures title at
Syros in April. Over the following months he tried unsuccessfully to qualify for the main draw of the
Gerry Weber Open in
Halle, the
Mercedes-Benz Cup in Los Angeles, and the
Canada Masters in
Toronto. He also
attempted to qualify for the
2002 US Open, winning against a fading
Cédric Pioline in the first round – this was technically a win by retirement, as Pioline stormed off court while 0-5 down in the third set. He lost in the next round of qualifying to Argentine
Gastón Etlis. He spent the bulk of the 2003 season playing on the
Challenger Tour and reached the semi-final stage of events in
Fergana and, after coming through qualifying,
Nottingham, where he lost to second seed
John Van Lottum. Chiudinelli began 2004 well, winning 18 of his first 22 matches. He won another Futures title in January in
Doha and the following month reached his first Challenger final in
Belgrade – along the way defeating a teenage
Novak Djokovic in one of his earliest professional appearances. Chiudinelli's ranking reached a then high of 129 in January 2005 after making the round of 16 at the
Qatar Open. He soon received his first call up to the
Switzerland Davis Cup team for the tie versus the
Netherlands, losing in five sets to the more established
Sjeng Schalken, and later winning the
dead rubber against
Peter Wessels. After retiring through injury in his second round match against
Michael Ryderstedt at
Wimbledon Qualifying in June, Chiudinelli was later forced to get surgery to heal persistent pain in his shoulder. As a consequence he did not play for the remainder of the season and his ranking fell to 287. At the
2010 French Open, Chiudinelli was accepted into the main draw by direct entry and beat
Somdev Devvarman to advance to the second round for the first time. There he lost to American
John Isner in a match that extended over two days because of rain.
Later career, 2015–2017 He also played the longest doubles match ever with
Stanislas Wawrinka, being defeated by
Lukáš Rosol and
Tomáš Berdych of the
Czech Republic in the first round of the
2013 Davis Cup. The match, played on 2 February 2013, lasted 7 hours, 2 minutes. Chiudinelli again represented Switzerland in the 2014 Davis Cup World Group first round, partnering
Michael Lammer. His doubles victory with Lammer clinched the first-round victory over Serbia, allowing Switzerland to advance to the quarterfinals for the first time since 2004. Switzerland went on to win its first Davis Cup in history. At the
2014 Gerry Weber Open in Halle, Chiudinelli played doubles with childhood friend and Roger Federer. They reached the final and held championship points, but lost a close tiebreaker. In 2016, Chiudinelli qualified for the
US Open and beat fellow qualifier
Guilherme Clezar in the first round in four sets. This was Chiudinelli's first main-draw Grand Slam tournament victory since the
2010 US Open. In the second round, he faced
Lucas Pouille. Chiudinelli was two sets and a break up in the third set and was serving for the match at 5–4, but was broken. He then lost the resulting tiebreaker and could not regain his form in the last two sets. Chiudinelli then received a wild card into the
2016 Swiss Indoors tournament where he took on compatriot Stan Wawrinka in the first round and lost in three sets 7–6(7–1), 1–6, 4–6, despite leading the match against the newly crowned 2016 US Open champion. In 2017, after an injury plagued-season, Chiudinelli announced on his website that he would be retiring following the
2017 Swiss Indoors tournament where he enjoyed the greatest success of his career, reaching the semifinals in 2009. ==ATP career finals==