MIAMI, March 29 (UPI) -- Spain's David Ferrer breezed into the quarterfinals at the Sony Ericsson Open Tuesday but American Mardy Fish had a tougher time dispatching Juan del Potro.
Ferrer, seeded sixth, defeated fellow Spaniard Marcel Granollers 6-1, 6-2 in an hour. Ferrer, who has two titles in hand this season, will face Fish in the quarterfinals.
Fish, seeded 14th, struggled to a 7-5, 7-6 (7-5) victory over del Potro, a former U.S. Open champion from Argentina.
Del Potro had beaten Fish in the semifinals at Delray Beach last month. Del Potro had reached the semifinals in four straight tournaments before losing Tuesday.
In other fourth-round matches set for Tuesday Rafael Nadal was to go against Alexandr Dolgopolov, Roger Federer was to face Olivier Rochus and Novak Djokovic was paired with Viktor Troicki.
Dolgopolov won his third-round match Monday night, eliminating France's Jo-Wilfried Tsonga, 6-7 (2-7), 6-4, 7-5 in a rain-postponed effort.
