Shanghai Open

The Serb former world number one began having issues in his left leg at the start of the seventh game

The world number two overpowered his German opponent in straight sets

38-year-old Swiss won 6-2, 7-6 (7/5) and plays Belgium's 13th seed David Goffin or Mikhail Kukushkin in the last 16

Finn tops early drivers' standings, showing why with lap of one minute 33.330secs

Swiss maestro defeated long-time arch-rival in straight sets at Shanghai Open on Sunday