Andre Agassi began his quest for a sixth title at the San Jose Open with a comfortable 6-4, 6-4 first round victory over qualifier Bobby Reynolds on Tuesday.
Third seed Tommy Haas also advanced with a 6-3, 7-6 victory over France's Gregory Carraz.
In his first match since losing to world number one Roger Federer in the Australian Open quarter-finals, the second seeded Agassi managed to wear Reynolds down from inside the baseline.
"It took a while to get comfortable, but ultimately I got my sense of court position and had my shots dialled in," Agassi said. "There were moments of real good tennis in Australia, but never when I really needed them.
"Here I'm hoping I'll see an arch to my improvement in the way I'm executing my game. Today was a little indecisive and I played too big of a shot at times."
The 34-year-old Agassi added the hip injury that nearly forced him to withdraw from the Australian Open was actually caused by a swollen nerve in his back.
"The nerve is recently swollen and the space in my back isn't as big as it used to be," Agassi said. "I need to reduce the swelling. But at least I'm clearer as to what the injury is."
Fourth seed Vince Spadea also advanced with a 5-7, 6-3, 6-2 victory over France's Anthony Dupuis while seventh seed Jurgen Melzer of Austria beat Glenn Weiner 6-2, 7-5 and James Blake beat South Africa's Wesley Moodie 6-3, 6-4.
Spadea, who reached the semi-finals of the Delray Beach tournament last week, said it took him a set to get used to playing indoors.
"I got off to a slow start, but then began to serve and return well," Spadea said. "I was happy to get the win."
Top seed Andy Roddick will play his first match on Wednesday against qualifier Paul Goldstein.