Rafael Nadal remains on course for a 12th Barcelona Open title after Friday's 7-5 7-5 victory over Jan-Lennard Struff sent him through to the semi-finals.

The 17-time grand slam champion needed an hour and 43 minutes to power past the German, who beat Stefanos Tsitsipas in impressive fashion in the last round.

Nadal recaptured some of his imperious best against compatriot David Ferrer after seeing a 30-set winning streak ended by Leonardo Mayer in the first round, and he looked to be cruising towards the last four when he opened up a quick-fire 4-1 lead in the first set.

Struff responded with a break of his own in game eight but a sloppy service game at 5-6 allowed Nadal to claim the set at the first opportunity.

Struff stuck to a bold serve-volley tactic to keep pace in the second, although he was unable to make any inroads into the Nadal service games, the 11-time champion winning 86 per cent of the points when his first serve landed.

After his opponent again opened the door at 5-6 down, Nadal clinched the win with his second match point, unleashing a spectacular forehand passing shot that landed right in the corner after Struff looked to have put a volley beyond his reach.

Nadal will face Dominic Thiem in the last four, with a final against Kei Nishikori or Daniil Medvedev awaiting the victor.

"I love to play against Nadal. And to play him on clay is one of the toughest challenges in our sport", mentioned Thiem after winning his quarterfinal match.