2009-2014: Early years Fratangelo has mainly played on the
ITF Pro Circuit since 2009. He played sparsely in both 2009 and 2010, before playing on a much more regular basis in 2011. He made his first final in July 2011 in the USA F17 event in
Pittsburgh, losing to
Brian Baker in straight sets. The following month, Fratangelo was given a wildcard for the
2011 US Open qualifiers, losing to
Fritz Wolmarans in the first round of qualification. He reached another final on the ITF Men's Circuit in May 2012, but lost in straight sets to
Tennys Sandgren in Tampa, Florida. In 2013, Fratangelo reached the semifinal in the USA F2 event in Sunrise, Florida, losing to eventual champion
Robby Ginepri, and then won his first professional title the following week, beating
Arthur De Greef in the final in Weston, Florida. He made his second final in as many weeks when he faced De Greef once again, but lost this time in Palm Coast, Florida.
2015-2017: First major match win and top 100 In April 2016, he won the
2016 French Open Wild Card Challenge by reaching the semifinals in
Sarasota and winning the
Savannah Challenger the following week. He put the wildcard to good use by defeating compatriot
Sam Querrey in the first round of the French Open to crack the top 100 for the first time. His ranking of No. 99 came out on June 6, 2016, which was the 60th birthday of the man he was named after,
Björn Borg. This was also his first career-match win in the main draw of a Grand Slam tournament. Fratangelo reached the semifinals at the
2017 Hall of Fame Tennis Championships.
2021-2023: Mixed doubles debut and first doubles win at the US Open He qualified for the main draw of the
2021 French Open, before losing to
Cameron Norrie. At the
2021 US Open, Fratangelo made his debut in mixed doubles with
Madison Keys, whom he began dating four years ago. He also paired in men’s doubles with
Christopher Eubanks as wildcards where he reached the second round recording his first win in doubles in his career at a Grand Slam over
Frances Tiafoe and
Nicholas Monroe. He secured his main draw spot at the
2022 French Open for a second consecutive year at this major with a straight sets win over
Nino Serdarušić. ==Coaching career==