Roger Federer & Novak Djokovic win openers in Miami

Roger Federer dropped just three points on serve in his opening match in Miami as he joined second seed Novak Djokovic in round three of the Sony Open.

Two-time champion Federer, given a first-round bye as the fifth seed, beat Croatia's Ivo Karlovic 6-4 7-6 (7-4).

Djokovic, 26, followed last week's win over Federer in Indian Wells with a 6-4 6-3 victory against Jeremy Chardy.

Defending champion Andy Murray defeated Matthew Ebden, while Venus Williams beat Anna Schmiedlova 6-3 6-3.

China's second seed Li Na progressed without hitting a ball when Alisa Kleybanova withdrew with a viral illness before their second-round match, while third seed Agnieszka Radwanska beat Romina Oprandi 6-0 6-4.

In the men's event, Federer is looking to regain the title he won in 2005 and 2006 after missing last year's tournament with a back injury.

"I was able to play a very clean match on my service games throughout, make sure I had a lot of first serves in, make sure I stayed aggressive from the baseline," said Federer after seeing off the 6ft 11in Karlovic.

"I think it worked really well, hardly any unforced errors. There are no long rallies. It's more like a penalty shootout in soccer.

Chardy required treatment in the latter stages against Djokovic

"It's about quick reaction, not getting frustrated and feeling that the returner is the one who has got less pressure."

Djokovic was held up before serving for the match when Chardy hobbled to a courtside entry tunnel with an ankle problem and took a medical timeout.

"He twisted his ankle," said Djokovic. "I talked with him after the match. He says it's not as bad as he thought, but I wish him [a quick] recovery."

Federer, 32, goes on to face Dutch qualifier Thiemo de Bakker in the last 32, while Djokovic will play German 30th seed Florian Mayer.

Fourth seed David Ferrer, ninth seed Richard Gasquet and 15th seed Grigor Dimitrov also made it through to the third round.