Grigor Dimitrov has rallied from a 4-1 second-set deficit for a 6-3 7-5 win over Juan Martin del Potro to reach the Cincinnati Masters quarter-finals.

The seventh-seeded Dimitrov had to tighten up his game to pick up his first career win in six matches against Del Potro. Dimitrov improved to 15-13 in his last 28 matches after opening the season 16-1.

“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.”

Dimitrov will face Yuichi Sugita, who advanced with a 6-7 (7-0) 6-3 6-3 win over Karen Khachanov.

David Ferrer reached his first ATP Masters 1000 quarter-final in his last 11 attempts with a 6-4 6-4 win over Pablo Carreno Busta.