KEY BISCAYNE, Fla. — Novak Djokovic is bouncing back nicely from a loss he called one of the worst of his career.

The Serb reached the quarterfinals of the Sony Ericsson Open by beating 21st-seeded Tomas Berdych 6-3, 6-2 Tuesday.

Djokovic, seeded third, has lost only 15 games in three matches since he endured a quarterfinal drubbing against Andy Roddick at Indian Wells 10 days ago. He 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.

In other fourth-round matches, fourth-seeded Andy Murray drubbed Viktor Troicki 6-1, 6-0. 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.

Roddick, top-ranked Rafael Nadal and Roger Federer had matches scheduled later in the day.