Saturday's other semi-final sends 22-year-old US newcomer John Isner - who beat German second seed Haas 6-4, 6-7, 7-6 - against 20-year-old fleet Frenchman Gael Monfils, who eliminated Russian third seed Safin 6-3, 7-5.

The final four average 6 1/2 feet tall with lanky Roddick the smallest.

"I'm sorry for bringing the height average down," Roddick said. Guys are getting bigger. I don't know if you can pigeonhole it just to tennis.

Roddick, the 2001 and 2005 Washington winner, improved to 40-10 for the year in quest of his 23rd career ATP title and second of the season after winning at Queen's in June.

Isner, in only his second ATP event, fired 30 aces to win his fourth match in a row by way of a third-set tiebreaker.

"I'm as confident as ever. I feel like I can beat anybody. My serves are going well and it's a great weapon," Isner said.

Monfils fired 14 aces and chased down shot after shot to defeat Safin as he did last year at Cincinnati in their only prior meeting.

Karlovic, ranked a career-best 41st, blasted 29 aces to avenge a loss at Memphis that launched Capdeville to his only prior ATP quarterfinal. The Croatian seeks his third crown of the year after Houston and Nottingham titles.

Isner ousted Britain's Tim Henman, German eighth seed Benjamin Becker, US qualifier Wayne Odesnik and Haas in last-set tiebreaks, losing the first set in each match until facing Haas.

"He kept me off balance but once again my serve kept me in the match," Isner said. "I'm not that nervous. I have nothing to lose out there. I can go out there and swing away.

He was fortunate to get into it. Isner only made the field because Chile's Fernando Gonzalez pulled out and made an extra wild card spot available.

Haas, who saved a match point in the second set, sent a forehand wide in the last tiebreaker to give Isner two more match points. Haas saved the first with an ace but Isner's service winner ended matters after two hours and 26 minutes.

Haas, playing his first event since pulling out of Wimbledon last month with a torn stomach muscle, joked that he wants an ATP ban on giants like Isner.

Haas, who was denied his 400th career ATP triumph, also wants to dump the Hawk-Eye replay appeal system, saying he could see a serve mark out but lost a challenge when he appealed to the computer system.

"It's not accurate at all. I found that out today," Haas said. "You can't call it Hawk-Eye because it's wrong.

"It's frustrating when you have a mark where you can really see it and the ref can see it and the Hawk-Eye calls it in. That's unfortunate."