Rafael Nadal (left) and Diego Schwartzman interact at the net after their match on Saturday in Rome, Italy. Photo: VCG

Rafael Nadal warned he knew how to fix his errors before his French Open title defense after crashing in the quarterfinals of the Rome Masters on Saturday, the final warm-up before Roland Garros.

The nine-time Rome winner slumped 6-2, 7-5 on a humid night in the Italian capital to Argentine Diego Schwartzman, a player the second seed had ­beaten in all nine of their previous clashes.

It was Nadal's last chance to tune-up before his bid for a 13th French Open, and record-equaling 20th Grand Slam to match Roger Federer in just over a week.

"It's a completely special and unpredictable year," said the 34-year-old.

"I'll probably go back home and then let's see what's going on. I did my job here. 

"I fought until the end. But losing that many serves, you can't expect to win a match.

"Something that I have to fix. I know how to do it. 

"I'm going to keep working and keep practicing with the right attitude and try to give me a chance to be ready.

"I did a couple of things well and other things bad. And that's it. At least I played three matches."

The two-time defending champion was making his comeback after a long coronavirus-enforced break having skipped the US Open.

Nadal beat fellow Spaniard Pablo ­Carreno Busta, a US Open semifinalist, 6-1, 6-1 in his first match this week followed by Serb Dusan Lajovic 6-1, 6-3.

But Schwartzman pulled out a stunning performance to leave Nadal with no answer.

"After such a long time without competing, I played good two matches, and now today I played a bad one against a good opponent," said Nadal.

"It was not my night, at all," he said. 

"Then we have to think internally why, how I can fix it."

Schwartzman, with just three career titles to Nadal's 85, said he had come close a few times to beating the Spaniard.

"I think four or five times I was close enough to feel like maybe if I play my best tennis I'm going to have chances," said the world No.15. 

"Also, he was coming back this tournament after seven months, more or less, eight months. 

"And I was thinking, OK, tennis, sometimes it's really crazy and I was not playing good, but ­today maybe I have the chance."