John Isner claimed a big scalp at the Paris Masters on Thursday, beating Roger Federer in a tight three-set encounter.
The American prevailed 7-6 (7-3) 3-6 7-6 (7-5) after two hours and 16 minutes, sealing the result on his fourth match point.
The match featured just one break, which went to Federer in the second set, but while the Swiss saved all six break points against him, he could not find another way past Isner's booming serve.
Isner bossed both tie-breaks, taking the first courtesy of a mishit Federer forehand and making the decisive mini-break in the second after forcing the Swiss into a backhand overhead miss at the net.
"At the US Open (where he beat Isner in the fourth round), I won my tie-breakers," Federer said. "Here, I lost them. It's a pity. I didn't play a bad match. I haven't been broken during six sets against him, and I lost the match. This is how it happens against John. It's always on his racquet, especially indoors."
Isner said: "This is a very big tournament. He's an incredible player. My favorite player and the greatest of all time, in my opinion. It was a huge win for me. I'm very proud I was able to get it done."
Isner moves on to face Spaniard David Ferrer, who saw off Grigor Dimitrov 6-7 (4-7) 6-1 6-4 in two hours and 20 minutes.
Ferrer has now beaten the Bulgarian in five of their six contests. He also has the upper hand over Isner, winning five of their six match-ups.
Elsewhere, fourth seed Stan Wawrinka advanced after beating Viktor Troicki 6-4, 7-5, while Tomas Berdych also reached the quarter-finals with a 6-3 6-4 victory over Jo-Wilfried Tsonga.