Top seed Andy Roddick eased into the quarter-finals of the San Jose Open with a 6-2, 6-3 win over Belgium's Kristof Vliegen on Thursday.
The American was joined in the last eight by compatriot Andre Agassi who had a tougher time overcoming South African Wesley Moodie 7-6, 6-4.
Agassi struggled against the big-serving Moodie, who nailed 21 aces.
Moodie pounded his way into a tiebreaker and held a set point at 6-5 only to err on a slice backhand.
Defending champion Agassi then ripped a forehand crosscourt passing shot to go ahead 7-6 and Moodie missed a forehand volley to close out the set.
In the second set, Agassi broke at love to 3-2 with a backhand passing shot.
The 24-year-old South African held a break point at 3-4, but missed a forehand sitter. Second seed Agassi won the match when Moodie again missed on a forehand.
"That's a big serve," Agassi said about his opponent. "His second serve I didn't have any problems with, but the first serve is coming from such a tall height that it doesn't have to be 120 miles per hour because he has such great direction on it.
"He serves real well to a spot and he served a high percentage. In the second set, he missed four first serves and that's the game I broke."
SEEDS LOSE
Agassi will play fellow American Jan-Michael Gambill in the quarter-finals.
Seeded players Robby Ginepri, Vince Spadea and James Blake lost their second round matches.
Seventh seed Blake was overpowered 6-4, 6-2 by Swede Joachim Johansson who hit 16 aces and never allowed the athletic American to seize control of the centre of the court.
"He plays very fast so I tried to play aggressive and take control the game. I served pretty well and didn't let him take control with his forehand," said 21-year-old Johannson, who will face Roddick, his former junior doubles partner, in the next round.
South Korea's Lee Hyung-taik knocked out sixth-seeded Spadea 2-6, 6-4, 6-4 and fifth seed Ginepri went down 3-6, 7-5, 6-4 to Frenchman Cyril Saulnier.
"When I came here I was sick," said Saulnier. "I had nothing to lose so I said to myself 'okay, so you're going to try to play your best.' So I was very relaxed, very concentrated on my game."
Saulnier will play American wildcard Robert Kendrick, who upset fourth seed Taylor Dent on Wednesday.