Top seed Roger Federer reached the Halle Open semi-finals on Friday, beating defending champion Florian Mayer 6-3 6-4 and edging closer to a ninth title at the Wimbledon tune-up event.

The 18-time grand slam champion, whose last title at Halle was in 2015, skipped the entire claycourt season after winning the Australian Open and claiming titles at Indian Wells and Miami this year, to prepare for grass.

He will now face rapidly rising talent Karen Khachanov, who won his all-Russian quarter-final against Andrey Rublev 7-6(8) 4-6 6-3 to reach his first tour semi-final of the year.

Federer, who has yet to drop a set in Halle after crashing out of Stuttgart in his first match back last week, limited his serve-and-volley game against the German who is a fine returner and Mayer was broken quickly as his opponent won the first set.

The 33-year-old Mayer squandered two break points at 1-0 in the second set and paid the price as Federer broke again and never relinquished his advantage to win in just over an hour.