Wimbledon champion Novak Djokovic struggled with a stomach issue as he came from a set down to beat Adrian Mannarino and progress in Cincinnati.
The 13-time Grand Slam winner defeated the French world number 28 4-6 6-2 6-1 to reach the third round.
Serbia’s Djokovic will next play Bulgarian Grigor Dimitrov, who beat Mischa Zverev 7-6 (7-5) 7-5.
“I didn’t have a great night and wasn’t feeling that well for the first set and a half,” said Djokovic.
“I’m just happy that I managed to overcome the challenge.”
Croatia’s Marin Cilic beat Marius Copil of Romania 6-7 (4-7) 6-4 6-4, while Robin Haase of the Netherlands defeated Germany’s Alexander Zverev 5-7 6-4 7-5.
Three-time Grand Slam winner Stan Wawrinka continued his return after knee surgery a year ago by beating Kei Nishikori 6-4 6-4, and Nick Kyrgios saw off Croatian Borna Coric 7-6 (7-1) 0-6 6-3.