Rafael Nadal remained on a collision course with Novak Djokovic by overcoming a first-set blip to ultimately comfortably dispatch Fabio Fognini and book a spot in the semi-finals of the Internazionali d'Italia.

The Spaniard may have feared a fourth consecutive last-eight exit in Rome when Fognini, who typically mixed brilliance with erraticism, fought back from 4-1 down to win the opening set.

But Nadal, a seven-time champion in the Italian capital, displayed his lasting quality on the clay to record a 4-6 6-1 6-2 victory and secure his ticket to the last four, where Djokovic or Kei Nishikori await.

In the process, Nadal stretched his head-to-head record over Fognini to 11-3 and maintained his hopes of returning to world number one after a quarter-final defeat to Dominic Thiem in Madrid saw him displaced by Roger Federer. 

Nadal earned break point in game four of the opening set when relentless pressure led to a forehand winner at the net, and some scarcely believable court coverage saw him put the chance away.

Fognini was unfortunate to find himself 4-1 adrift, but a huge forehand brought up three break points in game seven. Nadal saved those but could not hold off a fourth as another crunching forehand saw the Italian break back.

Incredibly, Fognini then turned the set around - a wild forehand from Nadal offered his opponent the break point and the Spaniard then went long with a backhand. 

Fognini easily held for the opener, but Nadal quickly rediscovered his groove, breaking in game two with a trademark powerful forehand and, when he broke again in game six, the set was out of his opponent's reach.

The writing was on the wall by the time Fognini gifted Nadal the first break in the deciding set in game three with a long forehand.

Nadal had the double-break lead when Fognini went wide on a backhand and the Spaniard went on to book a 10th last-four appearance in Rome.