STUTTGART, Germany (AP) -- Top-seeded Rafael Nadal posted his 91st win in 92 matches on clay to reach the semifinals of the Mercedes Cup with a 6-1, 6-3 win Friday against Argentina's Juan Monaco.
The Spaniard played with his right knee taped, but didn't seem bothered by an injury that flared up in his second-round match Thursday after first surfacing in the Wimbledon final against Roger Federer.
"At the start, I was a little unsure if the knee would hold up," Nadal said. "But then that passed and I played at really a very high level."
Nadal next faces his best friend on the tour, Spain's Feliciano Lopez, who upset sixth-seed Juan Carlos Ferrero, 6-4, 3-6, 6-4.
The second semifinal pits seventh-seeded Juan Ignacio Chela against Stanislas Wawrinka. Chela rallied from a set down to beat fellow Spaniard Fernando Verdasco 2-6, 6-3, 6-2, and Wawrinka eliminated Jiri Vanek, 6-1, 6-4.