Kei Nishikori of Japan advances to Memphis final

Matosevic couldn't continue, not with a bone bruise in his right foot making each step simply too painful.

Matosevic retired 37 minutes into his semifinal against Nishikori on Saturday, sending the Japanese player to the final of the U.S. National Indoor Championships. Nishikori called the quick end surprising because he didn't know Matosevic was injured.

"He was playing really well from the beginning and he broke my serve in the beginning 2-love," Nishikori said. "He was playing well, I thought. So I didn't think about he was retiring. Yeah, he's playing well this week. ... Things happen. But yeah, lucky for me to play just one set and feel fresh for tomorrow so I think it's good."

On Sunday, Nishikori will face Feliciano Lopez of Spain, a 6-2, 3-6, 6-3 winner over Denis Istomin of Uzbekistan. Lopez will be seeking his third title in his eighth career ATP final after a match he thought he had won with an ace — even preparing to shake hands with the chair umpire — only to replay the point because of a let ruling.

"In the old times, we had one guy on the net with a finger," Lopez said. "I don't know if it's more accurate or not. The system now with the machine you never know when it's real let or not."

Marina Erakovic of New Zealand won her first singles title Saturday night when Sabine Lisicki of Germany retired because of an illness in the last women's final in Memphis. The women's event, held in Memphis since 2002, is moving to Rio de Janeiro in 2013.

Erakovic lost this final to Sofia Arvidsson last year, and she took the first set Saturday night 6-1 in 27 minutes. During the break, Lisicki sat down and realized she couldn't continue.

"I just didn't have any energy left in the tank," Lisicki said.

Erakovic looked almost disappointed. The winner of seven doubles titles said she didn't realize Lisicki had been ill so she was shocked when the German retired and reacted as if on auto-pilot until she was handed the guitar-shaped trophy.