In his second round match against Leonardo Mayer on Wednesday, Nadal was well off his best, dropping the first in the tiebreak.
Nadal did improve to ultimately overcome Mayer but he made clear his unhappiness with he competed.
“It wasn’t the best start. Not the best feelings out there this afternoon, but I found a way to keep going and to win the match,” he said.
But there was no sign of sluggishness from Nadal against Ferrer as he won his 60th match at the Barcelona Open.
Nadal broke Ferrer three times in the second set to beat Ferrer, in what would be his last match at the tournament.
Speaking post-match to Spanish broadcaster RTVE, Nadal said improving his attitude was crucial to victory.
“I was the one who had to make an important improvement,” he said.
“The match with Mayer was tough and I had to take a step forward.
“Beyond what it means emotionally, I had to play with a different attitude than yesterday and I did.”
Nadal then took a moment to hail Ferrer, who he was playing for a 32rd time and in his last match at the Barcelona Open before retiring at next month’s Madrid Masters.
“He hasn’t been seeded, with tough draws and yet he’s been able to win very good matches,” he said.
“Anyway, it’s his decision, he’s been fighting for many years, giving us all so much joy and he deserves whatever he decides.”