Rio de Janeiro, Feb 19 (IANS): Spain's Rafael Nadal struggled to put away countryman Nicolas Almagro but eventually secured a 6-3, 7-5 second-round victory at the Rio Open to set up a quarterfinal clash against the Ukraine's Alexandr Dolgopolov.

The top-seeded Nadal needed one hour and 40 minutes to wrap up a second consecutive straight-set win at this clay-court tournament on Thursday, part of the ATP Tour's South American swing, reports EFE.

The World No. 5, who is trying to bounce back after a disappointing season in which he did not win any of tennis' biggest events, was mostly able to dictate play on Guga Kuerten Court.

Nadal was shaky toward the end of the contest, however, losing his serve twice in a row, including squandering a chance to serve out the victory at 5-4 and failing to convert two match points.

But Almagro was far less effective, losing his final three service games and winning only 59 percent of his first-serve points for the match, compared to 70 percent for Nadal.

Dolgopolov, Nadal's opponent in Friday's quarterfinals, rallied Thursday to defeat Spain's Iñigo Cervantes 3-6, 6-0, 6-3.

The eighth-seeded Dolgopolov has defeated Nadal in their past two matches, although the Spaniard holds a 5-2 career edge and won their only meeting in Rio de Janeiro, a straight-set victory in the 2014 final.