Blake, from nearby Fairfied, considers the Connecticut Tennis Center his home court and won the U.S. Open warmup in 2005. He beat Fernando Verdasco of Spain 6-4, 6-2 in the quarterfinals.

But for a while today, it didn't look like he'd make it that far. He lost the first set of his third-round match to Agustin Calleri of Argentina 3-6, and was down a break at 4-5, with Calleri serving for the match at 40-love.

With the crowd behind him, Blake finally figured out how to return Calleri's serve and began making big shots, including a passing volley while sprinting to the net at 40-15, prompting someone in the stadium to scream, 'Who's the fastest man in tennis?' "

After getting the break, Blake lost his next service game. But he broke right back to force the tiebreaker, which he won 7-2. He won the third set 6-1.

"I was easily just one first serve away from being out of here and on my way to Flushing Meadows," Blake said. "Now that I'm still in it, I feel great and I feel like I'm kind of lucky to be still at the tournament and still alive."

The men were forced to play two rounds Thursday after rain canceled numerous matches earlier in the week.

Top seed Nikolay Davydenko, No. 2 Tommy Robredo and No. 4 seed David Ferrer all fell early in the day.

Blake joined his best friend on tour, Mardy Fish, as Americans in Friday's semis. Fish beat Jose Acasuso of Argentina 6-7 (4), 6-3, 6-0 in his first match, before taking out Stanislas Wawrinka of Switzerland 6-3, 6-3 in the quarterfinals. Wawrinka had upset Robredo earlier.

"This was a huge test for me and my body to see if I was going to hold up," Fish said. "Stamina-wise I knew I was going to be fine. I've worked real hard off the court. Just didn't know if my knees were going to hold up. I figured they could hold up for a three-out-of-five set match, but could they hold up for three sets and then three more sets four hours later was the test, and I passed."

Fish will play Ivo Karlovic in the semifinals. The hard-serving Croat beat Igor Andreev of Russia 6-7 (8), 6-4, 7-6 (1).

Karlovic had 28 aces in the match, including 12 in the final set, when he hit 90 percent of his first serves in.

In the women's draw, Hungarian qualifier Agnes Szavay became the most unlikely entrant into the semifinals when she defeated No. 8-seed Alona Bondarenko 6-1, 6-4.

It was the sixth match in seven days for Szavay, who began playing in the qualifying round last Friday. She advanced to the quarterfinals after upsetting second-seeded Daniela Hantuchova Wednesday in the second round.

"I am very tired," she said. "If somebody would tell me before that I'm going to play the semifinal I would be really satisfied."

She will play Eleni Daniilidou of Greece, who upset Dinara Safina of Russia, 1-6, 7-6 (8), 6-2.

Daniilidou saved two match points in the tiebreaker, the last one on a shot that hit the net cord and dropped good.

"I was a little bit lucky I have to say," she said. "It was great points, long rallies. I was really happy with the way I played the second and third set. The first set I was not focused at all and not moving good."

Women's top-seed Svetlana Kuznetsova also advanced to the semifinals when Italian Francesca Schiavone retired with pain in her left ankle after Kuznetsova won the first set 6-2.

Schiavone said she didn't want to risk a more serious injury with the U.S. Open coming up next week.

"I prefer low risk," she said. "I prefer I take two days off, because when I run and I stop I feel pain."

Kuznetsova will play sixth-seeded Elena Dementieva. She advanced to her third semifinal of the year after defeating third-seeded Marion Bartoli, 6-4, 6-2.

Dementieva fought back from a 0-4 deficit in the first set, winning the next six games. She took command of the match in the sixth game of the second set, breaking Bartoli at love to take a 4-2 lead.

"I know that she likes to stay inside the court so it's very important to play deep against her," Dementieva said. "I was trying to stay on that game plan, and that really was helping me."

Blake will play Frenchman Paul-Henri Mathieu in his semifinal match. Mathieu beat countryman Gilles Simon 6-4, 6-3 in the final match Thursday night. He has never played Blake, and knows he will be the underdog.

"Everybody's going to be against me, but that's fine," he said. "If I play him in France, everyone's going to cheer for me, so it's OK."

Simon had beaten Davydenko earlier in the day 6-4, 6-4.

The Russian, ranked fourth in the world, did not play his first match of the tournament until Wednesday night, but said he did not feel tired until after the third-round match.