MEMPHIS, Tenn. » Kei Nishikori of Japan beat American qualifier Austin Krajicek 4-6, 6-3, 6-4 on Friday night in the quarterfinals of the Memphis Open.

Nishikori, ranked fifth in the world, shook off eight double-faults and struggled with unforced errors off his backhand. But Nishikori improved to 11-1 in Memphis by beating his friend in their first career meeting on tour.

"Obviously, I didn’t play my best tennis, but I still won today," Nishikori said. "That’s really important, I think. I won’t play every match my best tennis. I think it’s a very good win today because he was playing good tennis."

The two-time defending champ will play Sam Querrey, who upset No. 3 seed John Isner 7-6 (3), 7-6 (2), in the semifinals Saturday night.

Querrey improved to 3-1 against Isner in a match decided in the tiebreak between a pair of big servers. Isner had 12 aces and Querrey 13 with both winning nearly every point off their first serves. That left very few ground strokes, and Querrey said that made finding any rhythm tough.

"I’m sure a lot of people thought there were going to be some tiebreakers going into that," Querrey said. "It was just a couple points here or there. I got some stab returns, and that was basically it, literally just a couple points in each set."

Donald Young needed three sets to beat Bernard Tomic of Australia 7-6 (8), 4-6, 7-5 earlier Friday. He will play No. 2 seed Kevin Anderson of South Africa, a 6-4, 6-4 winner over sixth-seeded Steve Johnson.

Nishikori and Krajicek not only know each other, they also practice together. But Krajicek, who upset fifth-seeded Ivo Karlovic of Croatia on Wednesday, surprised Nishikori with his serve.

"He was hitting a lot of aces that I wasn’t really expecting," Nishikori said. "But I knew he’s been playing great. Beating Ivo is not easy, so I knew he was going to be a tough match."

Nishikori broke Krajicek in the eighth game of the second set and held serve to even the match.

He broke Krajicek again to open the third set, but Nishikori fought to hold serve in the sixth game of the third set after falling behind 15-40. Krajicek had four chances to break Nishikori in the game. Nishikori pushed the game to deuce, then finally converted on his fourth game point to go up 4-2.

Krajicek, who came into this week ranked 156th, broke Nishikori’s serve in the eighth game when Nishikori put a backhand into the net on break point. But Nishikori broke right back and served out for the match, his celebration delayed momentarily when he lost the grip on his racket before an overhead winner.

The finish left little to say between the friends. Krajicek said he was more comfortable on the indoor court playing his friend.

"But at the same time, playing a guy that’s (No.) 5 in the world isn’t easy no matter if you know him or not," Krajicek said.

Young, among five Americans in the quarterfinals at The Racquet Club, struggled with four double-faults in the second set. He bounced back by saving three of four break points in the third set to advance to the semifinals in Memphis for the first time. Young improved to 6-2 this year.

With the win, Young reached the fourth ATP Tour semifinal of his career as he looks for his first tournament title.

Anderson, in his second semifinal this year, needed only 65 minutes to defeat Johnson. The South African served up 16 aces and won 32 of 36 points on his first serve.