?Maria Sharapova of Russia returns a shot to compatriot Dinara Safina during their BNP Paribas Open match in Indian Wells on Tuesday

Roger Federer and Novak Djokovic rolled on at the BNP Paribas Open at Indian Wells, easily winning third-round matches on Tuesday while Kim Clijsters retired with a painful shoulder.

Clijsters' shoulder has bothered her since she won the Australian Open in January. She feels pain during her service motion and when she hits high forehands.

Women's top seed Caroline Wozniacki of Denmark beat Russia's Alisa Kleybanova 2-6, 6-3, 6-1, a victory, along with Clijsters' departure, that ensured the Dane will retain her No. 1 world ranking.

Federer defeated 29th-seeded Juan Ignacio Chela of Argentina 6-0, 6-2, and Djokovic routed Ernests Gulbis 6-0, 6-1.

Federer is 16-2 this year, while Djokovic has dropped just three sets during his 14-0 start, including his run to the titles at the Australian Open and Dubai.

"I'm very, very focused. Nowadays, I'm feeling great on the court, and I'm motivated to have more success," Djokovic said. "I just need to keep up, and that's what I'm trying to do."

Djokovic could knock Federer from the No. 2 ranking this week if he reaches the final or he reaches the semifinals and Federer loses before the quarterfinals.

Andy Roddick beat John Isner 7-5, 6-2 in an all-American night match, improving to 16-2 this year and making himself one of three US men still left.

Ryan Harrison defeated Canadian Milos Raonic 7-6 (1), 4-6, 6-4 in a pairing of wildcards. For winning his first ATP Tour match this year, the 18-year-old American earned a matchup with Federer in the fourth round.

Maria Sharapova advanced to the quarterfinals with a 6-2, 6-0 win over fellow Russian Dinara Safina under the lights.

Defending champion Jelena Jankovic lost to fellow Serb Ana Ivanovic 4-6, 2-6. No. 10 seed Shahar Peer of Israel outlasted fifth-seeded Francesca Schiavone of Italy 6-4, 3-6, 7-6 (3), and No. 8 Victoria Azarenka of Belarus got by No. 9 Agnieszka Radwanska of Poland 4-6, 6-3, 7-6 (3).