KEY BISCAYNE, Fla. — Andy Roddick is finding his way to the net for a change, which has helped him reach the quarterfinals at the Sony Ericsson Open.

Roddick won 22 points at the net and beat Gael Monfils 7-6 (2), 6-4 in the fourth round Tuesday.

The willingness to move forward is part of Roddick's more well-rounded game under Larry Stefanki, who became his coach in December. Roddick leads the ATP Tour in victories this year with a record of 26-4.

While the No. 5-seeded Roddick has improved his volley and backhand in recent months, he still possesses an overpowering serve and won 38 of 44 first-serve points against the No. 9-seeded Monfils.

Novak Djokovic also advanced to the quarterfinals, beating No. 21 Tomas Berdych 6-3, 6-2.

Roddick lost his serve for the only time to fall behind 6-5 in the opening set. He took advantage of three unforced errors by Monfils to break back and took control of the tiebreaker by smacking winners on the first two points.

"From the tiebreaker on I definitely felt like I was in control," said Roddick, who won the Key Biscayne title in 2004.

No. 8-seeded Svetlana Kuznetsova outlasted 18-year-old Caroline Wozniacki in the first women's quarterfinal, 6-4, 6-7 (5), 6-1. When the 2-hour, 54-minute match in humid, 80-degree sunshine ended, Kuznetsova slowly crumpled to the court in exhaustion and relief.

The 2006 champion will play in the semifinals Thursday against the winner of the match Tuesday night between No. 11 Victoria Azarenka and Samantha Stosur.

In other men's fourth-round matches, fourth-seeded Andy Murray routed Viktor Troicki 6-1, 6-0, and No. 10 Jo-Wilfried Tsonga won 6-7 (4), 6-3, 6-2 against No. 7 Gilles Simon, the highest-seeded man to be eliminated.

No. 6 Juan Martin del Potro beat No. 11 David Ferrer 6-3, 6-2. No. 8 Fernando Verdasco defeated No. 18 Radek Stepanek 6-2, 6-2 and will next face Murray.

The No. 3-seeded Djokovic has swept every set while losing only 15 games in three matches. His winning streak comes after a match Djokovic described as one of the worst in his career — a quarterfinal drubbing against Roddick at Indian Wells 10 days ago.

Djokovic broke serve five times against Berdych, who lost 15 of 24 points on his second serve.

"I knew he's very aggressive, but not really consistent from the baseline," Djokovic said. "He makes a lot of unforced errors, especially from the forehand side, so I changed the pace and I played really good tennis today."

Djokovic is seeking his second title at Key Biscayne. He won the tournament in 2007, then lost his opening match last year.