Alejandro Tabilo has pulled off a major upset…

The 27-year-old Chilean professional tennis player beat former World No. 1 Novak Djokovic 6-3, 6-4 in the second round of the Monte Carlo Masters.

Tabilo had previously handed the 24-time Grand Slam champion a surprising loss at the Italian Open last year.

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.

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.

The Monte Carlo Masters is the first big clay-court tournament of the year on the ATP Tour.