Rotterdam - Holder Juan Martin del Potro has tested his delicate left wrist over nearly one and three-quarter hours as he beat Gael Monfils 7-6 (8/6), 6-3 on Wednesday at the Rotterdam World Tennis.
The Argentine top seed repeated his win over the flamboyant and crowd-pleasing Frenchman from 2013 when he beat Monfils at the Ahoy stadium in their only other meeting.
Monfils came to the first-round start after winning a title at the weekend and has been beaten in 2014 only by Del Potro and Rafael Nadal in a 12-3 season.
Del Potro is dealing with recovery on his wrist which gave him pain at the Australian Open and sent him to an American specialist last month for consultations and a recovery programme.
"The wrist did well today," said the winner, who sent last week's Montpellier champion out on a second match point when he drove a forehand winner down the line.
"I'm hoping it continues this way. If I can keep playing like this I will have done good work. I'm very happy to be able to return and defend my title.
"Gael is a good friend of mine and a big fighter. It is always so tough to play him."
After starting off in somewhat poor humour on Kids day in a noisy stadium, Monfils settled in, matching Del Potro in long rallies and occasionally leaping for an overhead or throwing himself at a passing shot and rolling on the hardcourt.
Del Potro will next play another Frenchman in qualifier Paul-Henri Mathieu. The Argentine is a huge threat when he's top-seeded: in his last five tournaments at the top of the draw he has lifted five titles and has won 24 matches.
Two more seeds fought through to the second round as number four Frenchman Richard Gasquet beat Dutchman Thiemo de Bakker 6-7 (5/7), 7-6 (7/2), 6-3 and 35-year-old fourth seed Tommy Haas overcame Spain's Fernando Verdasco, Spain.
Nicolas Mahut of France reached the second round over lucky loser Daniel Brands 7-5, 6-3 while Austrian
Dominic Thiem put out Finnish veteran Jarkko Nieminen 6-4, 4-6, 6-4.
British second seed Andy Murray makes his start against Edouard Roger-Vasselin of France.
Results from the third day of the $1.3 million ATP World Tennis Tournament in Rotterdam on Wednesday (x denotes seeding):
Andy Murray (GBR x2) bt Edouard Roger-Vasselin (FRA) 6-3, 6-3
Juan Martn Del Potro (ARG x1) bt Gael Monfils (FRA) 7-6 (8/6), 6-3
Nicolas Mahut (FRA) bt Daniel Brands (GER) 7-5, 6-3
Tommy Haas (GER x6) bt Fernando Verdasco (ESP) 6-7 (4/7), 7-6 (7/1), 7-5
Richard Gasquet (FRA x4) bt Thiemo de Bakker (NED) 6-7 (5/7), 7-6 (7/2), 6-3
Dominic Thiem (AUT) bt Jarkko Nieminen (FIN) 6-4, 4-6, 6-4