Nadal, 32, lost a set at the event for the first time in four years in his win over Leonardo Mayer on Wednesday.

His struggles followed defeat by Fabio Fognini in Monte Carlo on Saturday, but here he dominated Ferrer.

The Spaniard will now play Jan-Lennard Struff after the German beat Stefanos Tsitsipas 6-4 3-6 6-2.

"I had to improve on yesterday, not just the result but overall," said Nadal, who needed four match points to seal the win.

"It was important to do better and play with more energy than yesterday. I did that so I can go back to my hotel feeling much happier."

Elsewhere, Japan's Kei Nishikori eased into the last eight with a 6-1 6-3 victory over Felix Auger Aliassime and will play Spain's Roberto Carballes Baena.