Question: Which tennis player won a major tennis championship in singles, Juan Martín del Potro or Bob Bryan?
Context: Adrian Mannarino (born 29 June 1988) is a French professional tennis player who is currently ranked world No. 31 in men's singles by the Association of Tennis Professionals (ATP).  He has a career-high singles ranking of world No. 27 (July 2015) and was the singles runner-up in three ATP World Tour tournaments - Auckland, Bogotá and Antalya.  Mannarino has achieved victories over Stan Wawrinka, Milos Raonic, Juan Martín del Potro, Gilles Simon, Juan Mónaco, Philipp Kohlschreiber and Gaël Monfils. Roger Federer was the five-time defending champion, but was defeated by Juan Martín del Potro in the final, 3–6, 7–6, 4–6, 7–6, 6–2.  This was del Potro's first major title. Juan Martín del Potro was the defending champion, but chose not to participate this year, after undergoing a wrist operation in May and only starting to practice again in August.  Del Potro was the third man in the Open Era not to defend his US Open title, after Ken Rosewall in 1971 (due to conflicts between the World Championship Tennis (WCT) and the International Lawn Tennis Federation (ILTF)), and Pete Sampras in 2003 (who unofficially retired after the 2002 final).  For the first time in U.S. Open history, no American player was seeded in the top 8, this was reflected in the result. On 24 August 2016, Roger Federer and Rafael Nadal were the first of six players to confirm their participation for team Europe.  On 15 May 2017, more than eight months later, Milos Raonic was the first of six players to confirm his participation for the World team.  By 24 August 2017, all six players from each team had been chosen: Roger Federer, Rafael Nadal, Alexander Zverev, Marin Čilić, Dominic Thiem, and Tomáš Berdych for team Europe, and Milos Raonic, John Isner, Jack Sock, Sam Querrey, Juan Martín del Potro, and Denis Shapovalov for team World.  Shortly afterwards Raonic withdrew and was replaced by Nick Kyrgios.  Later Frances Tiafoe took the place of del Potro who had also withdrawn. This is a list of the main career statistics of Argentine professional tennis player, Juan Martín del Potro.  To date, Del Potro has won 19 ATP singles titles, including one Grand Slam singles title at the 2009 US Open.  He was also the runner-up at the 2009 ATP World Tour Finals, a semi-finalist at the 2009 French Open and 2013 Wimbledon Championships, a quarterfinalist at the Australian Open in 2009 and 2012, a bronze medalist at the 2012 London Olympics, and a silver medalist at the 2016 Rio Olympics.  On January 11, 2010, Del Potro achieved a career high singles ranking of world No. 4 for the first time. Juan Martín del Potro (] , born 23 September 1988), also known as Delpo is an Argentinian professional tennis player who is currently ranked world No. 24 in men's singles by the Association of Tennis Professionals (ATP).  His biggest achievement has been winning the 2009 US Open, defeating Rafael Nadal in the semifinal and 5-time defending champion Roger Federer in the final.  He was the first to defeat both Federer and Nadal during the same major and was the only man outside the Big Four to win a major between the 2005 French Open and the 2013 US Open, a span of 35 tournaments.  He is also the second Argentine and the fifth-youngest man to win the US Open in the Open Era.  Other career highlights include winning the bronze medal in men's singles at the 2012 London Olympics and the silver medal at the 2016 Rio Olympics and being part of his country's successful Davis Cup team; but his career has also been hampered by a succession of wrist injuries. Denis Shapovalov (Hebrew: דניס שפובלוב‎ ‎ ; Russian: Денис Викторович Шаповалов ; born April 15, 1999) is a Canadian professional tennis player.  He reached a career-high ATP singles ranking of No. 51 on September 11, 2017, and a career-high ITF junior ranking of No. 2 on July 11, 2016.  Shapovalov won the 2016 Wimbledon junior singles title and the 2015 US Open junior doubles title with compatriot Félix Auger-Aliassime.  Shapovalov was a semifinalist at the 2017 Canadian Open, beating Juan Martín del Potro and Rafael Nadal during his run.  He plays for Canada, but holds both Israeli and Canadian citizenships. The 2013 ABN AMRO World Tennis Tournament (or Rotterdam Open) was a men's tennis tournament played on indoor hard courts.  It took place at the Ahoy Rotterdam arena in the Dutch city of Rotterdam, between 11 and 17 February 2013.  It was the 41st edition of the Rotterdam Open, whose official name is the ABN AMRO World Tennis Tournament.  The competition was part of the ATP World Tour 500 series of the 2013 ATP World Tour.  Second-seeded Juan Martín del Potro won the singles title. Michaël Llodra (] ; born 18 May 1980) is a French former professional tennis player.  He is a successful doubles player with three Grand Slam championships and an Olympic silver medal, and has also had success in singles, winning five career titles and gaining victories over Novak Djokovic, Juan Martín del Potro, Tomáš Berdych, Robin Söderling, Jo-Wilfried Tsonga, Nikolay Davydenko, Janko Tipsarević and John Isner.  Llodra has been called "the best volleyer on tour". Robert Charles Bryan (born April 29, 1978) is an American male professional tennis player.  He has won twenty-three Grand Slam titles: 16 in men's doubles and 7 in mixed doubles.  He turned professional in 1998.  With his twin brother Mike, he has been world No. 1 doubles player for much of the last several years, first achieving the top ranking in September 2003.  The brothers were named ATP Team of the Decade for 2000–2009.  The brothers became the second men's doubles team to complete the career golden slam at the 2012 Summer Olympics.
Answer: Juan Martín del Potro