MONACO -- Novak Djokovic's latest bid to win a 100th career title ended Wednesday in another shock defeat to a familiar face.
Alejandro Tabilo, who handed the 24-time Grand Slam champion a surprising loss at the Italian Open last year, beat Djokovic 6-3, 6-4 in the second round of the Monte Carlo Masters.
Back on clay for the first time since winning the Olympic gold in Paris last August, Djokovic said he didn't have high expectations going into the match.
"I expected myself at least to have put in a decent performance. Not like this, it was horrible," said Djokovic, who made 29 unforced errors. "I did not have high expectations. I knew I'm going to have a tough opponent, and I knew I'm going to probably play pretty bad. But this bad, I didn't expect.
"I was hoping it was not going to happen, but it was quite a high probability I'm going to play this way. ... A horrible feeling to play this way. Just sorry for all the people that have to witness this."
Tabilo clinched victory on his second match point when Djokovic hit a service return too long. Djokovic had saved one match point in the ninth game when he was trailing 5-3 and 30-40 on his serve, producing a neat drop shot over the net which his Chilean opponent couldn't reach.
The 27-year-old Tabilo has yet to drop a set against Djokovic. He joined Marat Safin and Jiri Vesely as the only players to have faced Djokovic more than once and not lost; all three hold a 2-0 record over Djokovic.
"It has been a tough year, so a little bit of the nerves were there," Tabilo said in an on-court interview. "I remembered last time what I did well, and thankfully I served well today and it helped me a lot. It was an unreal match."
A Monte Carlo title would have made Djokovic the only player to win each Masters event at least three times.
Djokovic, who recently lost the Miami Open final to Jakub Mensik, turns 38 next month -- shortly before the French Open starts on May 25.
French Open champion Carlos Alcaraz started his clay-court season by rallying for a 3-6, 6-0, 6-1 victory over Francisco Cerundolo.
The second-seeded Alcaraz was coming off a surprising loss to Belgian veteran David Goffin in his first match at the Miami Open.
Another upset seemed possible when Cerundolo, ranked No. 22, took the first set, but Alcaraz dominated the rest of the match and converted five of his seven break points across the second and third sets.
Alcaraz is seeking a second title of 2025 and to fine-tune his clay-court game ahead of a bid to retain his title at Roland Garros starting next month.
In other results Wednesday, Lorenzo Musetti, the 13th seed, beat Jiri Lehecka 1-6, 7-5, 6-2 to set up a last-16 match against fellow Italian Matteo Berrettini, who beat top-seeded Alexander Zverev on Tuesday.
Daniil Medvedev overcame Alexandre Muller 7-6 (6), 5-7, 6-2, and fourth-seeded Casper Ruud beat Roberto Bautista Agut 6-2, 6-1.
Richard Gasquet and Gael Monfils, a pair of 38-year-old Frenchman, were eliminated by Daniel Altmaier and seventh-seeded Andrey Rublev, respectively.
The Monte Carlo Masters is the first big clay-court tournament of the year on the ATP Tour.
The Associated Press and Reuters contributed to this report.