Rafael Nadal warned he knew how to fix his errors before his French Open title defence after crashing in the quarter-finals 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-equalling 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 practising 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 semi-finalist, 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."
Collated results from the sixth day of the ATP and WTA Italian Open in Rome on Saturday (x denotes seed):
Women
Quarter-finals
Simona Halep (ROM x1) bt Yulia Putintseva (KAZ) 6-2, 2-0 retired
Garbine Muguruza (ESP x9) bt Victoria Azarenka (BLR) 3-6, 6-3, 6-4
Marketa Vondrousova (CZE x12) bt Elina Svitolina (UKR x4) 6-3, 6-0
Karolina Pliskova (CZE x2) bt Elise Mertens (BEL x11) 6-3, 3-6, 6-0
Men
Quarter-finals
Diego Schwartzman (ARG x8) bt Rafael Nadal (ESP x2) 6-2, 7-5
Casper Ruud (NOR) bt Matteo Berrettini (ITA x4) 4-6, 6-3, 7-6 (7/5)
Novak Djokovic (SRB x1) bt Dominik Koepfer (GER) 6-3, 4-6, 6-3
Denis Shapovalov (CAN x12) bt Grigor Dimitrov (BUL x15) 6-2, 3-6, 6-2