8-time champ Federer beats Zverev for Halle quarterfinal

HALLE, Germany (AP) - Eight-time champion Roger Federer defeated Germany's Mischa Zverev 7-6 (4), 6-4 to book his quarterfinal place at the Gerry Weber Open on Thursday.

Federer, who is bidding for his 16th grass-court title, hit five aces and converted three of his four break opportunities to win the second-round match in an hour and a half. He did not face a break point.

The 35-year-old Swiss next plays defending champion Florian Mayer, another German, who upset the sixth-seeded Lucas Pouille 6-7 (6), 6-4, 6-3.

Third-seeded Kei Nishikori was forced to retire earlier with an injury during his match against Karen Khachanov.

The Japanese player was trailing 3-2 when he withdrew with a left hip problem.

Khachanov will next face Andrey Rublev in the quarterfinals. Rublev, who received a wild-card for the grass-court tournament, defeated Mikhail Youzhny 6-0, 3-6, 6-3.