Spain's Rafael Nadal advanced to the quarterfinals of the Brazil Open with a hard-fought 6-3, 6-4 victory here over Brazilian qualifier Joao Souza.

Just as he had at a clay-court event last week in Viña del Mar, Chile, the top seed showed during his opening singles match Thursday evening that he has mostly recovered from the knee injury that kept him out of action for several months but still needs more match play to rediscover his top form.

The 140th-ranked Souza won a surprising 86 percent of his first-serve points against one of tennis' best returners and also made the world No. 5 work to hold his service games during the contest, which lasted one hour and 18 minutes.

The players remained on serve for the first five games of the match, but a break in the sixth game gave Nadal a 4-2 lead and he served out the opening set three games later.

The second set was a tougher battle, as the Spaniard had to struggle to hold serve and did not break Souza until the ninth game.

Next up for the former world No. 1 in the quarterfinals will be Argentine Carlos Berlocq, a 7-6 (9-7), 6-4 winner over Spaniard Albert Ramos.

The 11-time Grand Slam champion pulled out of the Brazil Open doubles draw Wednesday, a day after he and Argentine David Nalbandian won their opening match, saying he wanted to avoid overtaxing his knee.

Nadal went off the ATP Tour after suffering a shock second-round exit at last year's Wimbledon at the hands of unheralded Czech Lukas Rosol, considered one of the biggest upsets in the history of that prestigious tournament.

He had planned to return to action in late December in Abu Dhabi, but a stomach virus forced him to withdraw from that exhibition tournament and he also pulled out of the recently concluded Australian Open.

The Brazil Open is the second of three Latin American clay-court events Nadal signed up to play in February.

The Spanish star was upset in the final of Viña del Mar - his first tournament back - by Argentina's Horacio Zeballos. He also is scheduled to participate in the Mexican Open later this month.

Known for his physically demanding style of play and outstanding defensive skills, the Spaniard has struggled to stay healthy during his career and has been forced to withdraw from each of the four Grand Slam events due to various injuries. EFE