Nadal had been out of action since the Australian Open
World number one Rafael Nadal made a successful comeback from injury to give Spain the perfect start in their Davis Cup tie against Belgium.
Nadal beat Ruben Bemelmans, ranked 144 in the world, 6-2 6-4 6-2 to give Spain a 2-0 lead.
It was his first match since damaging a leg muscle in his Australian Open quarter-final defeat by compatriot David Ferrer at the end of January.
Earlier, Fernando Verdasco beat Xavier Malisse 6-4 6-3 6-1.
World number nine Verdasco had replaced the injured Ferrer.
The doubles match in the best-of-five tie is on Saturday with the reverse singles on Sunday.
Nadal, the French Open, Wimbledon and US Open champion wrapped up victory in less than two hours in Charleroi when the Belgian went wide with an attempted winner.
"He (Bemelmans) is the kind of player who is a bit tricky, especially for me coming back from a period out of action with injury," Nadal said in an interview with Spanish television.
"I felt I was serving well, both on the first and second. I felt comfortable and I think that in general it was a pretty controlled match throughout."
Holders Serbia are tied at 1-1 with India after Asian and Commonwealth Games champion Somdev Devvarman defeated Janko Tipsarevic.
Viktor Troicki, who sealed his country's victory against France in December's 2010 final in Belgrade, put them into the lead in Friday's first singles match with Australian Open champion Novak Djokovic missing out.
He raced into a two-set lead over Rohan Bopanna, who then clawed his way back into contention to set up a cliffhanger which the Serb eventually won 6-3 6-3 5-7 3-6 6-3.
Devvarman then levelled the tie with a 3-0 defeat of Tipsarevic, although the Serb player dug deep, leading 4-1 in each of the opening two sets with the Indian winning 7-5 7-5 7-6 (7/3).
Serbia will be represented by their strongest pairing of Ilija Bozoljac and Nenad Zimonjic in Saturday's doubles where they come up against Bopanna and Devvarman.
India suffered a major blow to their chances after Grand Slam-winning doubles pair Leander Paes and Mahesh Bhupathi were forced to withdraw because of injuries.
Paul Capdeville of Chile claimed the biggest win of his career with a five-set victory over John Isner of the USA to level their tie up at 1-1.
Capdeville came from two sets to love down to beat Isner 6-7 (5-7) 6-7 (2-7) 7-6 (7-3) 7-6 (7-5) 6-4.
Joachim Johansson has endured a difficult time with injuries
Earlier, Andy Roddick improved his Davis Cup singles record to 32-11 when he beat Nicolas Massu 6-2 4-6 6-3 6-4.
World number four Robin Soderling and Joachim Johansson put in strong performances in front of their home fans to give Sweden a 2-0 lead over Russia.
Soderling beat Igor Andreev 6-3 6-3 6-1 before Johansson stunned Teymuraz Gabashvili to win 6-3 7-6 6-4.
Andreev, ranked 97th in the world, never came close to causing an upset but Johansson's win was a surprise.
Six years ago, Johansson was ninth in the rankings before a persistent shoulder injury led to his ranking plummeting to 749.
But he landed 33 aces and 73 winners on his way to beating the 76th-ranked Gabashvili.
Straight-set wins by Jeremy Chardy and Gilles Simon gave France a 2-0 lead over Austria.
Chardy gave the 2010 finalists an early lead by upsetting 10th-ranked Jurgen Melzer 7-5 6-4 7-5 and Simon outplayed Austrian veteran Stefan Koubek for a 6-0 6-2 6-3 victory.
Michael Llodra and Julien Benneteau could earn the decisive point for France in Saturday's doubles match against Melzer and Oliver Marach to set up a quarter-final meeting against either Croatia or Germany who are tied at 1-1 after day one.
Marin Cilic gave Croatia the perfect start with a five-set win over Florian Mayer but in another marathon encounter, Philipp Kohlschreiber levelled the match with a 6-4 3-6 4-6 7-6 (8-6) 6-4 victory over Ivan Dodig.
In Buenos Aires, David Nalbandian aggravated a groin injury and strained his lower leg in defeating Adrian Ungur 6-3 6-2 5-7 6-4 to help give Argentina a 2-0 lead over Romania
In the second singles match, Juan Monaco defeated Victor Hanescu 7-6 (7-5) 1-6 6-1 6-1.
Argentina will hope to wrap up victory in the doubles with Juan Ignacio Chela and Eduardo Schwank set to face Victor Hanescu and Horia Tecau.
A victory could save Nalbandian from playing reverse singles on Sunday.
The Czech Republic and Kazakhstan are level at 1-1 in their match in Ostrava after wins for home favourite Tomas Berdych and Andrey Golubev of Kazakhstan.