Stanislas Wawrinka of Switzerland lost a tight match to Novak Djokovic in the fourth round of the BNP Paribas Open tennis tournament at Indian Wells on Wednesday.
Djokovic of Serbia beat Wawrinka, ranked 16th, 7-6 (7), 7-6 (8).
Roger Federer, the world number two, took one hour and 49 minutes to see off 17th seeded Fernando Gonzales of Chile 6-3, 5-7, 6-2.
Federer's victory at the California resort sets up a quarterfinal with Fernando Verdasco of Spain.
"I'm looking forward to playing against Verdasco," the Swiss player said. "It's a good thing that I'm still in the tournament and facing an opponent who actually is going to extend the rallies a little bit."
Should he win at Indian Wells, Federer would become the only player to take the $4.5 million (SFr5.25) tournament four times.
He defeated Verdasco in their two previous match-ups.