Top-seeded John Isner beat fellow American Donald Young 7-6 (3), 6-4 on Thursday to move to the quarterfinals of Regions Morgan Keegan Championships.
Isner, ranked 14th in the world, used 22 service aces to dispatch Young in 1 hour, 43 minutes. They were on serve in the second set, when Isner broke Young for the match, the winner a forehand Young drove into the net.
Young did not have an ace in the match.
In the first set, Young broke Isner in the sixth game for a 4-2 lead. But Isner broke back in the next set, putting them back on serve.
"When I was up that break in the first set, it would have been nice to have held in the next game to see what happened,'' Young said, later adding: "There were only a few missed points, but at this level, it's only going to be a couple of points that are going to be the difference.''
Isner said he struggled early and was lucky to reach a tiebreaker in the first set.
"I didn't feel like myself from the get go,'' Isner said. "My feet were all over the place, I was out of position on every shot, and my forehand, which I rely on a lot, was pretty much missing.''
In the tie-breaker, Isner's serve reached 140-plus mph as he won the first set. He is now undefeated in eight tiebreakers this year. He was taken to a pair of tiebreakers in his opening win of the tournament over Gilless Muller of Luxembourg.
"That's usually when my adrenaline gets going the most,'' Isner said. "To have my serve as a weapon, it helps a lot in tiebreakers. I'm able to get cheap points. We're playing first to seven, so if I'm able to get to get two cheap points on my serve it puts so much pressure on my opponents. I find myself serving my best in the tiebreaker. I'm very comfortable, but I prefer not to play in them.''
Earlier, Sam Querrey beat seventh-seeded Kevin Anderson 7-6 (4), 6-4 to move into the quarters.
Querrey, the tournament's 2010 tournament and a wild card entry this week, will face No. 3 seed Radek Stepanek of the Czech Republic, who defeated American Ryan Sweeting 4-6, 6-3, 7-6 (4).
Querrey, who entered the week ranked 99th in the world, is on a climb back up the rankings after right elbow surgery last June.
Others advancing were Lukasz Kubot of Poland and Jurgen Melzer of Austria.
In the Memphis International, the women's side of the tournament, fourth-seeded Marina Erakovic of New Zealand was taken to three set before defeating Michaella Krajicek of the Netherlands 6-4, 6-7 (2), 6-4.
Other third-round winners Thursday in the women's draw were Sofia Arvidsson of Sweden, Alberta Brianti of Italy and Vera.Dushevina of Russia.