Top seed Andy Roddick came through with flying colours on a long day of double duty on Friday, downing Jan Michael Gambill 6-7, 6-4, 6-3 to reach the semi-finals of the Scottsdale Open.

Roddick's triumph was his second win of the day. Due to a wash-out on Thursday, he had played his second round match earlier on Friday morning, beating Alex Bogomolov 6-4 6-3.

Roddick will play fourth-seeded fellow American Vincent Spadea next

Spadea overcame compatriot and sixth seed James Blake 6-4, 2-6, 7-5.

But second seed Martin Verkerk wasn't as fortunate, upset by Victor Hanescu of Romania 7-5, 6-4.

Hanescu will face seventh seed Nicolas Kiefer of Germany, who beat third seed Robby Ginepri of the 6-3, 7-6 (8-6).

Roddick, who came into the tournament nursing a back injury, was frustrated with his inability to break Gambill in the first set and received a warning for hitting a ball out of the stadium in the seventh game.

He was unable to impose himself upon his former doubles partner and also argued with chair umpire and threw his racket.

"I felt like I was hitting the ball well, but I get to 15-15 point and miss a second serve return, or it would be 30-30 and I'd miss a passing shot," Roddick said.

PLAYING AVERAGE

"It's the little things that separate playing well from playing average. By no means was I playing badly, it was those little differences."

The 21-year-old was 0-2 against Gambill going into the match, but the reigning U.S. Open champion is a far different player now than the one who lost to Gambill in the 2002 Los Angeles semis.

"It's confidence," the third-ranked Roddick said. "I believe I can win out there, no matter how I'm playing or what I'm doing wrong.

"I believe I can find a way right now. That's the biggest difference. I feel I've improved my backhand. He used to really exploit that."

In the eight game of the third set, Roddick boomed four aces and didn't realise he had pulled off the feat. He then forced Gambill into a forehand error to win the match.

"I didn't know I hit four aces until I heard the crowd afterward and then I thought I must have done something," said Roddick, who served 11 aces to 21 from Gambill.

"The second point I didn't register as an ace. That's the first time I've ever hit four aces and not known it going into the last serve."

Verkerk began the day with a tough 6-2, 4-6, 6-2 win over American Cecil Mamitt, while his quarter-final opponent Hanescu defeated Robin Soderling 6-3, 6-7, 6-3.

The match between the 6ft 5ins (1.956 metre) Verkerk and the 6ft 6ins (1.981 metre) Hanescu never lacked in power, but it was the 22-year-old Hanescu who mixed in finesse and some ambitious net charges late in the second set to pull off the victory.

"I played my best tennis and served very well," said Hanescu, after reaching his first ATP semi-final.

"I was very focused. This is the beginning of my career. It's been my dream to be in a semi-final, to win a tournament, maybe a Grand Slam."

Kiefer, who reached the Memphis final two weeks ago after losing in the first round of his first four tournaments, said he has learned to enjoy the battle.

"I didn't play my best today, but I won because I was fighting," the German said. "To play good and win is easy but to play bad and win, that's a big challenge."