MEMPHIS, Tenn. -- Kei Nishikori of Japan finally has a chance to successfully defend an ATP Tour title. Ivo Karlovic of Croatia will be playing for his sixth career title coming off an even shorter match.
Fourth-seeded Yen-Hsun Lu of Taiwan retired Saturday from his semifinal because of a neck injury after losing the opening set 6-1 to Karlovic, ending the chance at an all-Asian final at the U.S. National Indoor Tennis Championships.
"It's going to be a tough opponent especially Ivo being indoors like this," Nishikori said of the chance to play Karlovic. "You don't get many returns easy. But we'll see."
Nishikori, who won his third career title here last year, needed only 64 minutes to beat American Michael Russell 6-3, 6-2 despite trailing 1-3 to the 35-year-old American at the start. Ranked 16th in the world, Nishikori improved to 10-2 this year.
"It's almost there," Nishikori said about defending a title. "Especially, like today I was playing good tennis and more confidence coming. It's going to be a tough opponent."
The No. 1 seed broke Russell's serve to tie the first set at 3-3, and Nishikori broke the American again and served out to take the first set in 34 minutes. Nishikori broke Russell again to start the second set and broke the American's serve to take a 5-2 lead before serving out for the match.
Russell upset former world No. 1 Lleyton Hewitt to reach only his third career ATP Tour semifinal. Unforced errors mixed with Nishikori's efficient serve kept Russell from what would have been his first final.
"He really played a high level," Russell said. "For me, I've played everybody. That was by far top-10, top-five level even after that middle of the first set. Everything that came off his racket was in the corner, an ace. It was very difficult. He was playing really well, and I wasn't able to get him out of that rhythm."
Nishikori won 22 of 28 points on his first serve (78 percent) in the match and was nearly perfect in the second set winning 10 of 11 points. The defending champ also served up six aces compared to only one for Russell.
"A couple double-faults but when the serve is good you can start well the points and you get good rhythm and you start playing well," Nishikori said. "The serve is really the key of the game."
The big-serving, 6-foot-11 Karlovic now has not been broken in 42 games this week, and he had seven aces in winning the set in 28 minutes. His last title came in Bogota last year, and he said he was really happy at finally reaching his first final at this event in his fifth trip to Memphis.
But Lu, trying to reach his second ATP Tour final this year, struggled enough he faced eight break points. Karlovic could tell from how Lu grimaced that he was in pain.
"When I knew he was hurting I just tried to put the ball in the court, and I was also a little bit lucky," Karlovic said. "I mean for him I know that it is difficult to have to stop, but injuries are part of tennis. I know. I had a lot of them."
Lu had been 8-2 this year and trying to reach his second final this year. He said he was eating breakfast Saturday when his neck locked up on him. He received four treatments trying to loosen up enough to play Karlovic. But Lu said the pain went down into his right shoulder and trying to finish the match at the risk of further injury didn't make sense.
"I don't think the fans like to see me not playing the best tennis out there," Lu said. "Then I decide to just walk out the court."