David Ferrer has claimed that his fourth-round encounter with Kei Nishikori at the Miami Masters will be "very difficult".

The Spanish third seed defeated Fabio Fognini 6-1 7-5 on Sunday to progress at the tournament in Florida.

"It's going to be a very difficult match," Ferrer said. "The last time I played him at the Australian Open I beat him in three sets, but I will have to run a lot.

"We will play a lot of rallies on the baseline. Nishikori, he has unbelievable shots. He plays with a lot of power."

Ferrer and Nishikori are currently tied at two matches apiece in their head-to-head record.