Andy Murray is through to the quarter-finals of the Western & Southern Open in Cincinnati with a 6-7 (3-7) 6-4 7-6 (7-2) win over American John Isner.
Britain's number one made a slow start, losing the first set on a tie break, but gradually played his way into the game against last year's runner up.
Eighth-seed Murray, 27, claimed the first break of the match early in the second set, which he won 6-4.
He then saved two match points before rallying to win the final set.
The Scot faces Roger Federer in the early hours of Saturday morning, UK time, after the Swiss world number three beat Gael Monfils 6-4 4-6 6-3.
"It was a big win for me because he plays very well here," said Murray.
"Returning his serve in these conditions is very challenging and I did well to fight back. I felt I played a very good match. When challenged at the end I felt I responded well."
After losing to Jo-Wilfried Tsonga in the Rogers Cup quarter-finals in Toronto last week, Murray is looking for wins ahead of the US Open, which begins on 25 August.
Top seed Novak Djokovic suffered another blow to his hard-court season with a straight sets defeat by Spaniard Tommy Robredo 7-6 (8-6) 7-5.
The world number one, who lost to Tsonga in Toronto last week, said: "Just many, many, many things are not clicking these two weeks on hard courts.
"It's unfortunate, but it's more than obvious I'm not playing even close to what I'm supposed to play. I have to keep on working and trying to get better for the US Open.""
Third seed Stan Wawrinka beat Marin Cilic 3-6 6-1 6-0, sixth seed David Ferrer beat Mikhail Youzhny 7-5 6-0, and fifth seed Milos Raonic beat American Steve Johnson 6-7 (7-9) 6-3 7-6 (7-4).
In the women's draw, number one seed Serena Williams beat Flavia Pennetta 6-2 6-2 and will face eighth seed Jelena Jankovic in the next round.
Simona Halep and Maria Sharapova will meet in another of the enticing quarter-finals.