LOS ANGELES -- Defending champion Andre Agassi needed just 54 minutes to defeat Robby Ginepri 6-3, 6-1 at the Mercedes-Benz Cup on Thursday night.

Agassi, the No. 2 seed, broke Ginepri twice in each set. His own serve overwhelmed his 19-year-old opponent, and Agassi served two consecutive love games in the first set.

"I felt I was on top of my game early, putting pressure on and controlling the points,'' said Agassi, playing his first tournament since losing in the second round at Wimbledon.

"The last couple of matches I've answered a few questions. I'm feeling better the last couple of days,'' he said.

Ginepri had only one break point against Agassi in the match, but couldn't convert and committed three straight errors to fall behind 5-3 in the first set.

"He is pretty tough. He got me from the go,'' Ginepri said. "I didn't put as many returns in play as I wanted to. He hits the ball so deep and consistent. He served so well and I couldn't get into any sort of rhythm.''

Agassi advanced to a quarterfinal against No. 5 Gustavo Kuerten, a semifinalist here last year, who beat Britain's Martin Lee 7-5, 7-6 (5). It was Kuerten's second hardcourt victory since last year's U.S. Open.

Kuerten's match was delayed 30 minutes in the second set when a male spectator had a seizure and convulsions in the grandstand at the Los Angeles Tennis Center.

The unidentified 41-year-old man was stable and alert when he was taken to UCLA Medical Center, where he was being kept for evaluation, said Dr. George Fareed, the tournament physician.

Kuerten said the delay didn't bother him, although he later had triple match point and let two of them go.

American Alex Bogomolov Jr., a qualifier playing in his first ATP Tour event, lost 6-3, 6-3 to German Nicolas Kiefer. Two days earlier, Bogomolov stunned Kiefer's countryman, top-seeded Tommy Haas.

"Tommy lost to him, so I had to fight back for Germany, and I did,'' Kiefer said.

Jan-Michael Gambill is the forgotten man when talk turns to possible American successors for aging superstars Agassi and Pete Sampras.

He beat Israel's Noam Okun 7-6 (2), 6-2 to advance to the quarterfinals in Los Angeles for the third consecutive year.

"I want to get my confidence back to where I was at the Ericsson Open,'' said Gambill, who lost in three sets to world No. 1 Lleyton Hewitt in the round of 32 at the Florida tournament in March.

"If I get there, I feel I can beat anybody. Getting that kind of confidence just comes with matches.''

Now 25 years old, Gambill finished last year with an ATP ranking of 21st. But it certainly wasn't based on the final months of the year, when a right shoulder injury kept him sidelined for 15 straight events.

"I'd still be a top 15 player if I wasn't injured last year,'' he said. "That kind of thing is very difficult to deal with.''