Davydenko fell to Juan Monaco of Argentina 6-2, 6-7 (5), 6-4, and Roddick lost to wildcard Gael Monfils of France 7-5, 6-3.

Fourth-seeded Lleyton Hewitt advanced after defeating Diego Hartfield of Argentina 6-2, 6-2, and will play Monfils in the semifinals. Luis Horna of Peru beat Albert Montanes of Spain 7-6 (5), 6-7 (2), 6-1.

Davydenko never found his rhythm against the 47th-ranked Monaco after trailing 4-0 in the first set.

The top-seeded Russian still won a tight second set, but Monaco dominated the third and converted his first match point.

"Monaco got off to a quick start which made it very hard to fight my way back into the match," Davydenko said. "I was almost exhausted after winning the second set, and had not enough power left for the third."

Monfils, ranked 75th, combined eight aces with strong forehands and drop shots from the baseline against Roddick.

"Normally you win the point when you hit the ball in a corner three times — but not so against Monfils," Roddick said. "He's a great athlete and seems to get every ball back."

The 20-year-old Frenchman is coming back after seven months out with foot and ankle injuries.

"I am very happy with my performance this week — it is a real confidence booster for me," Monfils said. "I knew how to play Roddick as I beat him last year. I am tall and can reach a lot of his serves."

Monfils advanced to his first semifinal since the ATP Masters Series in Rome in May, when he beat Roddick in the quarterfinals.

Roddick was broken for the first time in the tournament while serving for the first set at 5-4. Another break by Monfils earned him the opening set.

Roddick, who missed three break points in the first game of the second set, was broken in the next game and received a warning for smashing his racket to the court.

Roddick missed two more chances on Monfils' serve at 4-1 down.

Hewitt broke Hartfield two times to build a 3-0 lead in the first set.

"It was very important for me to start well and put him under immediate pressure," Hewitt said. "I just wouldn't allow him to play his usual game."