Stan Wawrinka won a see-saw contest against Grigor Dimitrov at the Western and Southern Open in Cincinnati.
Wawrinka prevailed 5-7 6-4 7-6 (4) but that was only half the story as the Swiss struggled to serve out the match.
Dimitrov was 5-1 down in the final set but clawed back to level - saving two match points in the process - and force a tie-break decider.
Wawrinka raced to a 4-0 lead in the tie-break and, despite handing back two mini-breaks, he steadied to close out a fifth successive win over Dimitrov with a 138 miles per hour ace.
Roger Federer also secured his place in the next round with a 6-3 6-4 win over Juan Londero in just over an hour, while Novak Djokovic came through against Sam Querrey 7-5 6-1.
Two-time Next Gen ATP Finals qualifier Andrey Rublev surprised number 15 seed Nikoloz Basilashvili 6-7 (4) 6-4 6-2 to set up a second-round meeting with Wawrinka.
Daniil Medvedev overcame Kyle Edmund for the second time in six days with a 6-2 7-5 success.
Medvedev beat Edmund at the Rogers Cup in Montreal last week and won the final four games to book a last-32 date with Benoit Paire, of France.
Paire progressed when his Spanish opponent Fernando Verdasco withdrew after losing the first set 6-4.
There were also first-round wins for American pair Reilly Opelka and Frances Tiafoe, David Goffin, Denis Shapovalov and Diego Schwartzman.
