Top seed Swiss tennis player Roger Federer knocked out the current champion of Halle Open, German Florian Mayer, and advanced to the semi-final of the tournament.

Federer, an eight-time winner in Halle, took just over one hour to beat Mayer 6-3, 6-4 in the tournament played on grass on Friday, Efe news reported.

Federer, who is seeking his ninth title, will next play against Russian Karen Khachanov, who beat his compatriot Andrey Rublev 7-6 (8), 4-6, 6-3.