WASHINGTON (AP) _ Top-seeded Andy Roddick struggled before advancing past 14th-seeded Juan Ignacio Chela of Argentina in three sets at the Legg Mason Tennis Classic on Thursday night.
Roddick won 85 percent of his first-serve points and took advantage of nine double-faults by Chela to win 6-4, 6-7 (4), 6-4. Clearly frustrated throughout the match, Roddick was able to win despite an admittedly below-par performance.
"Tonight was one of those nights where you feel like you're on the verge of playing well,'' said Roddick, who will face unseeded Ivo Karlovic of Croatia in Friday's quarterfinals. "In a tournament, you always have a match where you win with stuff that's maybe not your best.
"I feel like I'm hitting the ball well. Now I just need to find my playing form.''
The hard-hitting Karlovic advanced to the quarterfinals with a 7-6 (4), 6-2 win over 11th-seeded Greg Rusedski of Britain. Karlovic had 14 aces in the match, bringing his tournament total to 60, and won 95 percent of his first-serve points in knocking off his second straight seeded opponent.
"It was hot, and I think in the second set he was a little bit tired,'' the 6-foot-10 Karlovic said. "I think that I am playing well here, and I am happy that I am in the quarterfinals.
In Karlovic, Roddick will face a player he says boasts the most difficult serve on the ATP tour.
"His serve is probably the biggest weapon in tennis,'' said Roddick, who defeated Karlovic in straight sets in the championship match at The Stella Artois Championships in London two months ago. "You can't teach being 6-foot-10. It's like he's serving out of a tree. Just the angles that he's able to create, he makes you hit his serves over your head where you're normally hitting them from around your hip.''
Earlier on Thursday, Paradorn Srichaphan overcame 15 aces by Wesley Moodie of South Africa in a 6-3, 7-6 (1) victory to advance to the quarterfinals. Paradorn, seeded 13th, won just 20 hours after playing through stomach pains in a three-set win over Paul Goldstein.
Unseeded players James Blake, Luis Horna of Peru, Arnaud Clement of France and Bobby Reynolds and 10th-seeded Thomas Berdych of the Czech Republic also advanced to the quarterfinals. Blake, the 2002 tournament champion, will look to get past the quarterfinals of a tour event for the first time this season when he faces Clement on Friday night.
In the other quarterfinal matches, Paradorn will meet Horna, and Berdych will meet Reynolds.