The world number five, building up to an assault on an eighth Wimbledon title in July, will next face Karen Khachanov, who defeated fellow Russian Andrey Rublev 7-6 (10/8), 4-6, 6-3 in his last-eight clash.
This is published unedited from the IANS feed. "I'll prepare myself the best I can, but he's definitely the favourite in that match".
Despite a shock exit from Stuttgart on his comeback last week, Federer has improved in Halle and has not lost a set.
"I thought it was extremely close, especially that second set".
Federer fired his 11th ace for a 5-3 and was unable to convert on three match points in the next game, with Mayer saving them all.
Roger Federer, 35, who is playing his 13th consecutive semifinal, will use his experience against younger rival Alexander Zverev. Federer has won 12 of his last 19 final appearances overall. "I'm feeling excellent and it's a pleasure to be back", said Federer, who skipped the clay-court season to rest.
"It's tough to play against a friend like Lucie", Kvitova said.
Zverev did finally set up a break point on the Federer serve in the first game of the second set, but it passed by and Federer raced on to complete victory.
"I played unbelievably well".
Switzerland's Roger Federer, right, with the victor trophy and Germany's Alexander Zverev, left, with the trophy for the second place, frame model Eva Herzigova, after the final match of the Gerry Weber Open tennis tournament in Halle, Germany, Sunday, June 25, 2017.
"I played against a right-hander from the baseline in Sugita, a left-hander who serves and volleys all time (Zverev) and Mayer plays very differently to everyone else".
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