Roger Federer moved a step closer to winning a ninth Gerry Weber Open title by beating Mischa Zverev to reach the quarter-finals after Kei Nishikori suffered another injury setback just 11 days before Wimbledon gets under way.
Federer suffered a shock loss to Tommy Haas in his first match on grass this season in Stuttgart last week, but followed up a straightforward win over Yuichi Sugita by beating Zverev 7-6 (7-4) 6-4 in Halle on Thursday.
The 18-time grand slam champion did not face a single break point in the second-round match and came out on top in a tie-break to get his nose in front, before breaking once in the second to set up a meeting with defending champion Florian Mayer.
Zverev got himself out of a hole by saving three break points before levelling at 5-5 in a tight opening set, but two sumptuous backhands from the top seed made the difference in the breaker.
The second set went with serve until Federer scampered across to fire a forehand at the body of Zverev, which he had no chance of returning and the Swiss broke to lead 5-4 before serving out the match as he eyes a fourth title of the year with Wimbledon fast approaching.
Nishikori's progress has been hampered by injuries and the third seed was 3-2 down in his first grass-court tournament of the year when he retired from his encounter with Karen Khachanov due to a back problem.
The world number nine was plagued by a wrist injury for much of the clay-court campaign and, although he reached the quarter-finals at the French Open, he has not won a title this year.
Mayer was a 6-7 (6-8) 6-4 6-3 victor over sixth seed Lucas Pouille, while wildcard Andrey Rublev beat Mikhail Youzhny in an all-Russian second round match and will now face another compatriot in the form of Khachanov.