HALLE, Germany (AP) Roger Federer will bid for a record eighth Gerry Weber Open title when he plays Italy's Andreas Seppi after advancing Saturday to his 10th final.

Federer defeated big-serving Ivo Karlovic 7-6 (3), 7-6 (4) while Seppi won the other semifinal after second-seeded Kei Nishikori pulled out with a left calf injury when the Italian was leading 4-1.

''I hurt it yesterday during the match and fought through but felt a bit of pain today. With an injury it's never easy to win and I didn't want to take a big risk for Wimbledon,'' Nishikori said with an eye to the tournament starting in nine days.

''I cannot say much because I have to see how the pain goes. I'm sure it'll be OK. It's no big deal,'' the Japanese player added.

Seppi also had a short quarterfinal on Friday when fourth-seeded Gael Monfils pulled out with a right knee injury as the 45th-ranked Italian led 6-1, 1-0.

''It's the first time it happened to me so we'll have to see how it affects me tomorrow,'' Seppi said of his lack of match practice.

''I'll try to take a few positive memories with me (from the final),'' said Seppi, whose only victory over Federer came at the Australian Open in January. ''I think it's 11-1. I'm certainly not the favorite.''

In contrast to Federer, Seppi was playing his first semifinal in his sixth appearance at Halle.

Federer won just five points on Karlovic's serve in the first set but made a mini-break to go 4-3 up in the first tiebreaker. He won the set on Karlovic's double-fault.

In the second tiebreaker, Federer correctly challenged a call that would have put Karlovic ahead 4-3 and secured another mini-break when Karlovic hit a return into the net. He took the first of two match points to wrap up the match in 1 hour, 28 minutes.

''I'm relieved to have got through the match. It was always my aim to defend the title,'' said Federer, who will be going for his third straight at Halle.

Karlovic was not broken all week and the eighth-seeded Croat hit 45 aces in Friday's quarterfinals, an ATP record for a best-of-three-sets match.

He had 20 aces on Saturday but couldn't prevent Federer from moving a step closer to claiming his 15th title on grass.

''Sometimes you can't do anything,'' Federer said of Karlovic's serve. ''You have to hope for a bit of luck or that you don't make a mistake at an important moment. The whole match can change in a moment. Thankfully it went well, though I had a bit of luck in the tiebreak.''

The 17-time Grand Slam winner's only losses in the final at Halle came against Lleyton Hewitt in 2010 and Tommy Haas in 2012.