Sao Paulo, Brazil, 18 February 2013 | AFP

Rafael Nadal showed he is back in business by clinching his first title since ending a seven-month knee injury layoff, winning the Brazil Open on Sunday.

The Spanish former world No.1, who has yet to fully shrug off the lingering effects of his knee problems, beat Argentina’s David Nalbandian 6-2 6-3 in 78 minutes.

Currently the world number five, Nadal went on the attack from the start, breaking his opponent’s service before racing to take the first set.

The 31-year-old Nalbandian, a former world No.3 who now languishes at No.93 in the ATP rankings, fought back early in the second set but Nadal came from behind to win, sparking wild cheers from the crowd.

The Spaniard pocketed a check for $US82,300 ($A80,000) for his win and thanked the public for “the great support” he received throughout the tournament.

Nadal was the top seed in this $US455,775 ($A442,500) tournament, his second comeback event following his long absence.

He competed in the Vina del Mar Open in Chile earlier this month, losing the singles and doubles finals last Sunday.

“It’s a great title and important for me,” said the 26-year-old.

“Yesterday (during the semifinal) the knee hurt. Today it’s better, rather bearable. I am happy to win in Brazil for the second time.”

The world No.5, who has 11 grand slam titles under his belt, first won the event in 2005, when it was held in Costa do Sauipe in eastern Bahia state.

Asked about his future plans, Nadal, who now has 37 claycourt titles in a 51-trophy career haul, replied: “I am going to think about Acapulco (later this month) and nothing else.”

As to whether he feels confident enough now to compete against the world’s top three of Novak Djokovic, Roger Federer and Andy Murray, Nadal said: “We are going to see how the knee responds and then take stock.”

“I don’t have any problem playing against better rivals because I accept that I can lose. Losing is not a problem for me,” added Nadal, whose last title was his record-breaking seventh French Open victory in June.

“I just need time to continue improving and return to a more competitive level.”

Considered by many to be the best ever claycourt player, Nadal was back on the court in Chile earlier this month for the first time since suffering a surprise second-round exit at Wimbledon in June.

Since then he had been sidelined by a torn tendon and inflammation in his left knee, with his return this year further delayed by a stomach virus.

His absence ruled him out of the Olympics, the US Open as well as January’s Australian Open.

Earlier Sunday, Brazilian Bruno Soares teamed up with Austrian Alexander Peya to win the Sao Paulo doubles final against Frantisek Cermak of the Czech Republic and Slovak Michal Mertinak 6-7 (5-7) 6-2 10-7.