Isner escapes but injury ends Nishikori's bid at ATP Delray Beach
John Isner of the US, pictured during the Heineken Open tournament in Auckland, New Zealand, on January 11, 2014 - by Michael Bradley
Isner, playing his first event since a right ankle injury forced him to retire from his first match at the Australian Open, rallied to down Israel's Dudi Sela 3-6, 6-1, 7-6 (7/5).
Into the last eight at Delray for the third year in a row, Isner will next face US qualifier Rhyne Williams, who eliminated Cypriot Marcos Baghdatis 6-7 (7/9), 6-4, 6-2.
Japanese third seed Kei Nishikori, coming off his fourth career ATP title last week at Memphis, retired with a left hip injury.
The 24-year-old Asian, now coached by retired US star Michael Chang, trailed 4-2 to Russian Teymuraz Gabashvili when he pulled out of the match after 18 minutes and indicated it might be a long-term setback.
"I had been feeling it before my first match and I played through it," Nishikori said. "But I just couldn't do anything today. It didn't get better. It's going to take some time to recover."
Nishikori helped Japan defeat Canada in a first-round Davis Cup tie earlier this month after reaching the fourth round of the Australian Open last month, losing to world number one Rafael Nadal.
Gabashvili, seeking his first title at the $474,000 event, advanced to a quarter-final against Croatian seventh seed Marin Cilic, who eliminated American Ryan Harrison 6-3, 6-4 in 74 minutes.
Isner seized a 4-1 lead in the third set and had four match points in the 10th game before Sela rallied to hold.
"If I'm up 4-1 in the third set more times than not I close it out," Isner said. "He got a lot of returns back blocking them back and spun his web on me when we were both on the baseline. It definitely didn’t need to be 7-6 in the third. It puts a lot of stress on me playing matches like that but I always seem to do it. But I’m glad to get through."
Isner, 5-0 in third sets this year, improved to 8-2 in tie-breakers after falling behind 5-2 in the decider.
Cilic has won 10 of his past 11 matches, taking his 10th career ATP title two weeks ago on home soil at Zagreb and losing in the final last week at Rotterdam to Czech Tomas Berdych.
"It was another good win," Cilic said of his win. "It wasn't easy, a lot of wind, but I was putting the ball in the right places and I think my serve worked well in the critical moments. That's always important."