Top seed Borna Coric earned a hard-fought victory Wednesday at the Winston-Salem Open to reach his sixth tour-level quarter-final of the season.

The 26-year-old Croatian survived wild card Michael Mmoh 6-4, 6-7(3), 6-3 in two hours, 47 minutes. Coric fired 11 aces and struck the ball with conviction to reach the last eight, where he will next face Argentine Juan Manuel Cerundolo. World No. 29 Coric has played his best tennis under pressure this week, having saved 16 of 17 break points he’s faced across two matches.

“I started to play better in the second set. He was serving really, really big and I didn’t have a chance to break him [in the second set],” Coric said. “Overall I thought it was a good match from my side and also from his side. I’m very happy with my level of tennis and I hopefully I can keep on getting better.”

Aiming for his fourth tour-level title and first since last year’s surprise run at the ATP Masters 1000 event in Cincinnati, Coric is making his third appearance in Winston-Salem, where he has twice reached the last eight (2015, 2017). His quarter-final contest against Cerundolo, who downed lucky loser Omni Kumar 7-5, 6-3 in third round, will mark his first encounter with the Argentine.

“I need to check him out a bit. I did watch him play a couple of times, but I’ve never watched him play where I was focussed on his game,” Coric said. “I need to check him out on YouTube and Tennis TV to see how he plays and then decide all of my game plans.”

Fifth seed Jiri Lehecka also needed three sets to advance Wednesday, defeating German Dominik Koepfer 6-3, 3-6, 6-4. Fourth seed Laslo Djere cruised past American wild card Alex Michelsen 6-4, 6-4 after winning 76 per cent of points behind his first delivery to close the night. Djere will next meet sixth seed Sebastian Baez, while Lehecka will clash against Australian Max Purcell in the quarters.