World No.1 Rafael Nadal stormed into the quarter-finals of the ATP Rio Open on Thursday by hammering Spanish compatriot Albert Montanes 6-1 6-2.

Nadal, in his first event since losing last month’s Australian Open final, needed only 74 minutes to book a last-eight clash with the winner of a later match between Portugal’s 48th-ranked Joao Sousa and 87th-rated Spaniard Albert Ramos.

Nadal broke Montanes three times in each set while surrendering his lone service break in the second set as he improved to 3-0 all time against his countryman, having yet to lose more than three games in any set against him.

A nagging back injury that has hindered Nadal since his Melbourne loss to Swiss Stanislas Wawrinka forced the 13-time grand slam champion to skip Buenos Aires last week.

That left his comeback for the $US1.3 million ($A1.45 million) event in Rio, where he starts a claycourt season that he hopes will culminate in a ninth career French Open crown.