Acapulco - Rafael Nadal's injury comeback gathered pace on Thursday as the 11-time Grand Slam champion reached the semi-finals of the Mexican Open and inched closer to a possible title showdown with fellow Spaniard David Ferrer.
Nadal, playing his third tournament in four weeks after a seven-month injury layoff, beat Argentina's Leonardo Mayer 6-1, 7-5 in the quarters and will now play Nicolas Almagro.
Ferrer, the top seed and three-time defending champion whose world number four ranking puts him one spot higher than Nadal, breezed past Italy's Paolo Lorenzi 6-3, 6-1 to book a semi-final clash with Fabio Fognini.
The tournament is one of three Latin American clay court events Nadal tabbed for his comeback from a left knee injury.
He opened with a runner-up finish at Vina del Mar - his first tournament since a surprise second-round exit at Wimbledon in June -- and followed up by lifting the title in Sao Paulo two weeks ago.
And he has insisted this week that he is still planning to play the upcoming hard court Masters Series events at Indian Wells and Miami, although he continues to experience pain in his knee.
Nadal won the first set against Mayer with relative ease, but the Argentine stepped it up in the second, and had two break chances against Nadal in the third game that he was unable to convert.
Mayer was also steadier on his own serve in the second frame, with Nadal unable to gain a chance to break until the 10th game, when the former world number one made an impressive sliding backhand winner to give himself a match point against Mayer's serve.
Mayer delivered a service winner and went on to hold for 5-5. But in the 12th game his inopportune double fault gave Nadal a double-match point. Mayer saved one with an overhead winner, but could not fend off the next.
"This was a very difficult match," Nadal said. "Leonardo was playing really well in the second set, he began to play more aggressive and his serve was working well."
Ferrer went down an early break against Lorenzi but bounced back quickly and broke the Italian five times en route to the victory in 72 minutes. He next faces another Italian in Fognini, a 7-5, 6-4 winner over Colombia's Santiago Giraldo.
Nadal's next opponent Almagro, a two-time winner in Acapulco, beat Horacio Zeballos of Argentina 6-3, 6-4, firing down 10 aces in the 70-minute encounter.
Almagro's win denied Nadal the chance for revenge against Zeballos, who beat the Spanish number two seed in the Vina del Mar final.
In the women's quarter-finals of this combined ATP and WTA tournament, top seed and defending champion Sara Errani defeated Kiki Bertens of the Netherlands 6-4, 6-4.
Second-seeded Spaniard Carla Suarez Navarro also advanced, downing sixth-seeded Italian Francesca Schiavone 6-7 (5/7), 6-4, 6-2.
Results from the fourth day of the ATP and WTA Acapulco tennis tournament on Thursday (x denotes seeding):
David Ferrer (ESP x1) bt Paolo Lorenzi (ITA) 6-3, 6-1
Fabio Fognini (ITA) bt Santiago Giraldo (COL) 7-5, 6-4
Nicolas Almagro (ESP x3) bt Horacio Zeballos (ARG x8) 6-3, 6-4
Rafael Nadal (ESP x2) bt Leonardo Mayer (ARG) 6-1, 7-5
Sara Errani (ITA x1) bt Kiki Bertens (NED) 6-4, 6-4
Carla Suarez Navarro (ESP x2) bt Francesca Schiavone (ITA x6) 6-7 (5/7), 6-4, 6-2
Alize Cornet (FRA x3) bt Lourdes Domínguez Lino (ESP x7) 3-6, 7-6 (12/10), 7-6 (7/2)
Silvia Soler Espinosa (ESP) bt Karin Knapp (ITA) 6-2, 6-2