MIAMI (REUTERS) - Roger Federer overcame a sluggish start to defeat Filip Krajinovic 7-5 6-3 and Kevin Anderson's booming serve proved too much for Joao Sousa as both seeded players advanced to the fourth round of the Miami Open on Monday (March 25).

Serb Krajinovic broke Federer to jump into an early 2-1 lead in the first set and it looked like an upset could be in the works against the 20-time Grand Slam champion.

But momentum swung in the fourth-seeded Federer's direction when he blasted a cross-court forehand winner to break Krajinovic's serve to take the closely fought first set.

The 37-year-old Swiss coasted after that thanks to an overpowering serve that Krajinovic struggled to read.

Next up for Federer is a clash with either American qualifier Reilly Opelka or Russian Daniil Medvedev, who were playing their third-round contest when Federer's match ended.

Anderson mixed 13 aces with just one double fault to seal a 6-4 7-6(6) victory over Portuguese Sousa earlier on Monday.

The towering South African sixth seed will be a heavy favourite on Tuesday when he faces unseeded Australian Jordan Thompson, who beat Grigor Dimitrov 7-5 7-5.