World number one and defending champion Roger Federer rallied from a set and a break down to beat Ernests Gulbis 3-6, 6-1, 6-4 to secure a spot in the Madrid Masters semifinals on Friday.
World number two Rafael Nadal followed a much easier path to the semifinals with a comfortable straight sets win over Frenchman Gael Montfils.
Federer lost to Gulbis last month at the Rome Masters in his first clay-court match of the season, and the Latvian looked set to repeat the upset until the top-ranked Swiss found his stride in the second set.
Federer will play ninth-seeded David Ferrer, who beat 2008 champion Andy Murray 7-5, 6-3.
Switzerland's Roger Federer celebrates his victory over Ernests Gulbis of Latvia during their Madrid Open tennis tournament May 14, 2010.
Nadal needed just one hour and 17 minutes to reach the semifinals for the second year in succession.
Nadal is undefeated on clay this season with a 13-0 record, having won titles in Monte Carlo and Rome and is looking for a record 18th Masters title. Nadal and Andre Agassi have won 17 each, with Federer on 16.
Nadal will meet fellow Spaniard Nicolas Almagro in the semis after Almagro's easy win over Austrian Jurgen Melzer.