Juan Martin del Potro toiled for over three hours before subduing Feliciano Lopez in his first tour match for almost a year at the Sydney International on Monday.
The giant Argentine, who downed Roger Federer in the 2009 US Open final, got just the workout he needed when he ousted the 32nd-ranked Spaniard, 6-7 (5/7), 7-6 (11/9), 7-6 (7/3) in a first round match.
Del Potro has not played on the tour since the Australian Open last January, when he needed right wrist surgery and was sidelined for eight months.
"I feel good for all my match, and finally I won a match after one year," he said.
Del Potro, currently ranked at 258, will have a protected ranking of No.5 heading into next week's Australian Open in Melbourne because of his recovery time on the sidelines.
"It was good tennis before the Australian Open, but I still want to win here. I'm ready to fight again."
Del Potro's next opponent will be Germany's Florian Mayer, who dealt with English wildcard James Ward in straight sets.
The Argentine, 22, who got wildcard entry into the Sydney tournament, said he was not surprised at how well he stood up to the physical test -- playing for 3hr 20min at the Ken Rosewall Arena in warm conditions.
"I worked very hard for two months in Argentina. My coaches trust in my condition and I trust myself, so I'm ready again to play long matches," he said.
"I will see how I feel after tomorrow, but I have my physical trainer here and my coach. They know how I can be better for my next match."
Del Potro said to beat a high-ranked player like Lopez had given him renewed confidence heading into the new season after his injury nightmare.
"I'm still feeling like it's a long road to play better," he said.
"Today I beat one top-30 player. If I can play with them, maybe in the future I can play like I did two years ago with the top 10 players."
Defending champion Marcos Baghdatis pulled out of the Sydney International with a groin injury.
Baghdatis, who beat Frenchman Richard Gasquet in last year's final, said he did not want to risk the injury ahead of the year's first Grand Slam tournament in Melbourne.
"It's been four days I have pain," 21st-ranked Baghdatis said. "I don't want to risk too much by going in the match and making it worse, so I took the decision today with my team not to participate here.
"I've been working on it with my physio, but I just don't want to risk it with the Australian Open coming on."
Cypriot Baghdatis, 25, who lost to Federer in the 2006 Australian Open final, will be replaced in the Sydney men's draw by lucky loser Lukasz Kubot of Poland, who goes straight into the second round.