Novak Djokovic is through to his first ATP Tour quarter-final of the season after beating Albert Ramos Vinolas in straight sets in Rome.

The former world number one has struggled for form and fitness this year, yet followed up a comprehensive victory over Nikoloz Basilashvili on Wednesday with another positive display on clay.

Djokovic showed glimpses of his best form in a routine 6-1 7-5 triumph that sets up a last-eight showdown with Kei Nishikori at the Internazionali d'Italia.

A four-time champion who also reached the final of the tournament last year, the Serbian knows he needs a good run in the Italian capital after slipping down to 18 in the world rankings.

He wasted little time in making an impact against Ramos Vinolas, breaking in his opponent's opening service game as he raced through the first set after just 32 minutes on court.

The second was more of an even contest, however. Djokovic had to work hard to move a break up but failed with his first opportunity to serve out for the match.

Ramos Vinolas' aggressive approach with nothing to lose allowed him to surprisingly draw level at 5-5, only for last year's finalist in Monte Carlo to then immediately lose his next service game.

Djokovic made no mistake at the second attempt, sealing a sixth successive win over the Spaniard with his solitary ace of the match.

Next up will be a last-eight clash with Nishikori, who needed just over an hour to see off German Philipp Kohlschreiber 6-1 6-2 and set up a rematch with the player who knocked him out in the opening round of the Madrid Open.