Roger Federer reaches semi-finals at Gerry Weber Open in Halle
Roger Federer beat Florian Mayer to reach the semi-finals of the Gerry Weber Open in Halle, Germany.
Switzerland's 18-time major winner, 35, beat his 33-year-old German opponent, the defending champion and world number 134, 6-3 6-4.
World number five Federer will face Russian 21-year-old Karen Khachanov, the world number 38, in the next round.
The other semi-final will be between Richard Gasquet and Roberto Bautista Agut or Alexander Zverev.
After losing to 39-year-old Tommy Haas in his first match in two months at the Stuttgart Open earlier in June, Federer is yet to drop a set at Halle, where he is bidding for a ninth title.
The seven-time Wimbledon champion has won three titles so far this season, including the Australian Open - his first Grand Slam success in five years.
Federer also won the BNP Paribas Open at Indian Wells in March and, two weeks later, the Miami Open.
In May, he announced he would be missing the French Open and the rest of the clay-court season to concentrate on the grass and hard-court seasons.