Grigor Dimitrov reached the Western & Southern Open quarter-finals with a comfortable straight sets victory over Juan Martin del Potro in Cincinnati.
The world No 11, who has already secured two ATP World Tour titles this year, had never beaten the experienced Argentinian in five previous encounters but rallied from a 4-1 second-set deficit for a 6-3 7-5 win in intense heat on Thursday.
The former US Open champion threatened a comeback when he earned a set point to take the match to a decider, however, the 26-year-old Bulgarian held firm to secure victory in one hour and 39 minutes and book a meeting with Japan’s Yuichi Sugita.
“I played pretty sloppy for the first three games,” Dimitrov said of the second set. “It was all my fault. I just thought if I stayed with him and made the right decisions, I would have a chance.”
Sugita, the world No 46, upset NextGen star Karen Khachanov 6-7(0) 6-3 6-3 to reach his first ATP Masters 1000 quarter-final in two hours.
Veteran Spaniard David Ferrer was another player to progress to the quarter-finals – his first at the ATP World Tour Masters 1000 level since the 2015 Paris Masters – and showcased his never-ending drive for top-level tennis with a confident victory over compatriot and 11th seed Pablo Carreno Busta.
Ferrer, the word No 31, holds a 11-2 record since Wimbledon and will next meet Dominic Thiem or Adrian Mannarino for a place in the semi-finals.
NextGen contender Jared Donaldson continued his fine run in Cincinnati with a straight sets win over Georgia’s Nikoloz Basilashvili.
The 20-year-old world No 60, a wildcard recipient, secured a 6-4 7-6(4) victory in one hour and 36 minutes and awaits the winner of the all-American clash between Frances Tiafoe, who shocked Alexander Zverev on Wednesday, and 14th seed John Isner.