HALLE, Germany -- Roger Federer progressed to the semifinals of the grass-court Gerry Weber Open without playing after Lu Yen-hsun of Taiwan pulled out of their quarterfinal with back problems on Friday.
Federer, who began his preparations for Wimbledon by defeating Portugal's Joao Sousa on Thursday, compensated by playing an exhibition against Christopher Kas, a German player who is 78th in the doubles rankings.
Kohlschreiber recovered from a 2-5 deficit in the tiebreaker before claiming the win in 2 hours, 10 minutes.
"I don't think a third set ever went so long," the 2011 tournament winner said. "Absolute war of nerves. ... The atmosphere was incredible but in the end you just want to leave the court as the winner."