Former US Open winner Juan Del Potro struggled to defeat Portugal's world number 488 Pedro Sousa as the big Argentine made an unconvincing start to his claycourt season at the Estoril Open on Tuesday.
Del Potro, who played only three events in 2010 due to right wrist surgery, emerged a 6-2, 3-6, 6-3 winner after nearly two hours, with qualifier Sousa putting in a respectable showing for the home crowd.
Sousa, 22, playing his first match at the ATP level, took a set off the former top five player and saved two match points - the second with a canny lob - before finally falling.
Along the way, he out-aced Del Potro six to four and broke the eighth seed twice.
Del Potro is playing this week on clay for the first time this season after resting following his hardcourt outing in Miami.
The Argentine is trying to play his way into form with the French Open now less than a month away from May 22.
After winning the first set, life got difficult for Del Potro, who lost serve in the second to trail 3-5 before Sousa served out to level the sets. In the third, it took a big effort from the seed to go through.
He finally wrapped up the win on a third match point as Sousa returned wide.
Del Potro moved into a second-round clash with Colombian Alejandro Falla, who advanced as Spain's Pablo Andujar retired injured at 4-6, 6-1, 4-4.
Del Potro currently ranks 48th after sinking to a low of 484 in early February. He began to build comeback momentum by taking a title at Delray Beach on hardcourt and reached semi-finals at San Jose, Memphis and Indian Wells.
French third seed Jo-Wilfried Tsonga, who made a publicity visit in the morning to an old-style classic Portuguese sailing ship, will open his Estoril debut with a match against Pablo Cuevas.
The Uruguayan booked his place with a 6-2, 6-4 win over Spaniard Per Riba.
Frenchman Gilles Simon, seeded fourth, will start in the second round after a bye against another South American in Carlos Berlocq, who beat Daniel Gimeno-Traver of Spain 6-4, 6-3.
Spanish second seed Fernando Verdasco will aim for a win in his first appearace in eight years at the venue when he plays local Frederico Gil, who put out Italian Flavio Cipolla 6-3, 6-2.
On the women's side, three seeds advanced but number four Anastasija Sevastova of Latvia lost to Pole Ursula Radwanska 5-7, 7-6 (7/5), 6-1.
Going through to the second round were second seed Jarmila Gajdosova, who beat Czech Renata Voracova 6-4, 6-0 and number three Klara Zakopalova, a winner against Beatriz Garcia Vidagany by 6-4, 7-6 (7/3).
Eighth-seeded Hungarian Greta Arn beat Portugal's Maria-Joao Koehler 6-2, 3-6, 6-3.