Swiss Stan Wawrinka overcame battling Bulgarian Grigor Dimitrov 5-7 6-4 7-6(4) in a roller-coaster first-round match at the Cincinnati Masters on Tuesday.
Dimitrov clawed back from a double break down in the decider to level at 5-5 and after Wawrinka broke again, Dimitrov forced the tiebreak.
The Swiss surged into a 4-0 lead but Dimitrov rallied once more before Wawrinka closed out the match with an ace.
American Frances Tiafoe beat Frenchman Gael Monfils 7-6(7) 6-3 and Canadian Denis Shapovalov came from behind to see off Portugal's Joao Sousa 2-6 6-3 6-2.
Georgia's Nikoloz Basilashvili, the 15th seed, and 16th- seeded Belgian David Goffin also progressed.
Basilashvili ousted Russia's Andrey Rublev 7-6(4) 4-6 6-2 and Goffin stopped American Taylor Fritz 6-4 4-6 6-4.
Top seed Novak Djokovic meets Sam Querrey and number three Roger Federer plays Juan Ignacio Londero later on Tuesday.
