Tournament favourite and second seed Andy Roddick scraped through to the semi-finals of the Nasdaq-100 Open with a 5-7, 6-2, 7-5 win over last year's runner-up Carlos Moya on Thursday.

In the women's draw, top seed Serena Williams continued her rehabilitation from a long layoff, easing through to the final with a 6-4, 6-4 victory over Greece's Eleni Daniilidou.

Roddick twice stared defeat in the face against the former French Open champion when the Spaniard served for the match at 5-4 in the third set and had a break-point on the American's serve at 5-5.

"I don't know how I pulled it off," a relieved Roddick said.

"He was the better player for much of the match. He let me back in. It's as simple as that. He got a little bit tight.

"I would love to sit here and claim all the credit and say I was fighting hard and all but that really wasn't the case. He gave me a gift of a game at 5-4 and I was able to tough it out after that," Roddick added.

"When you have these chances against Roddick and you don't take them, normally you lose," Moya lamented. "That's what happened today."

Ironically it was Roddick's record-breaking serve which repeatedly got him into trouble, wilting in the breezy conditions and allowing Moya to consistently put the American under pressure.

Despite his troubles, Roddick did send one booming delivery down at 145 mph, just five miles per hour off his serve speed record.

After dropping a tight first set, Roddick was the better player in the second but all looked lost when he dropped serve at 3-2 in the third.

When the Spaniard didn't take his chances at 5-4 ad 5-5, Roddick punished him for his profligacy, mustering up a match-point at 6-5 and taking it with a smash which bounced over Moya's head.

"Sometimes you lose a match like this and you don't know what to think," Moya said.

"I was controlling the match very well and probably I got tight and that was it."

Roddick now plays Vince Spadea, who beat him en route to winning the Scottsdale title last month.

The unseeded Spadea continued his hot streak of form by beating Andre Agassi's conqueror Agustin Calleri of Argentina 7-5, 6-1.

Spadea, who has been overlooked by U.S. Davis Cup captain Patrick McEnroe in favour of Mardy Fish for the next week's quarter-final tie against Sweden, has now won 11 of his last 12 matches.

SERENA ADVANCES

Williams, playing her first tournament after eight months out with a knee injury, raced into an early lead and wrapped up the first set despite some powerful hitting from the Greek.

The second set was not so straightforward for the American. She lost her own serve when 5-3 up but broke back immediately to wrap up the match in an hour and 23 minutes.

"I always expect the best of myself," Williams said. "I can't say that I didn't expect to be in the final, I can only say that I didn't want to lose in the first round.

"Physically this is great, but mentally it's awesome. I am really proud of myself because it's hard to come back."

"It was a good tournament for me," Daniilidou said.

"I really tried to enjoy the match today and I did, but Serena was just serving too good and I was under pressure from the first point."

At one stage, Daniilidou became so frustrated with being aced that that she gave up altogether and handed her racket to a ballboy. Williams responded with another ace on the next point.

The top seed will play Elena Dementieva in Saturday's final after the fifth seed eased past fellow Russian Nadia Petrova 6-4, 6-2 in the late match.

Dementieva, who beat Venus on Wednesday, will be bidding to become the first player since Kim Clijsters in 2002 to defeat both Williams sisters at the same tournament.

Only three players have managed the feat, the others being Martina Hingis in 2001 and Lindsay Davenport in 2000.

"I think it's a great chance for me to play against both of them in the same week and feel the difference between them," Dementieva said.

"It's a great experience to see what I can do against Serena. She's one of the best players in the world. I have nothing to lose."