Defending champion Roger Federer reached the final eight of the ATP Cincinnati Masters on Thursday after a walkover match against Germany's Philipp Kohlschreiber.

The German pulled out of the third-round match citing a right shoulder injury.

Federer, the 16-time Grand Slam champion from Switzerland, has not yet finished a set in the three million-dollar hardcourt event after a first-round bye and a 5-2 lead when Uzbek qualifier Denis Istomin retired with an injury in the second round on Wednesday.

Federer will face the winner of a later match between Russian sixth seed Nikolay Davydenko and Spain's David Ferrer on Friday for a berth in the semifinals of the last major U.S. Open tuneup.