Nadal, Nishikori into Miami quarters

Rafael Nadal and Kei Nishikori moved into the quarterfinals of the Miami Open with victories at Key Biscayne on Tuesday.

Nadal beat France's Nicolas Mahut 6-4, 7-6 (7/4) in a tightly fought contest and will face American Jack Sock who comfortably beat his compatriot Jared Donaldson 6-2, 6-1.

The Spaniard, who has never won the Miami title, got the only break of the match to go 5-4 up in the first set.

Second-seed Nishikori, of Japan, survived a second set scare against Argentine Federico Delbonis before winning 6-3, 4-6, 6-3.

Nishikori, who lost to Novak Djokovic in last year's Miami final, will face Italian Fabio Fognini who defeated American Donald Young 6-0 6-4.

Czech Tomas Berdych, the tenth seed, also advanced thanks to a 6-3, 7-5 victory over France's Adrian Mannarino.

Later on Tuesday, in-form Roger Federer, who has won the Australian Open and Indian Wells this year, is up against Spain's Roberto Bautista Agut while compatriot Stan Wawrinka plays Germany's Alexander Zverev.