Novak Djokovic says he is facing up to a "new reality" after losing his opening match for the second successive tournament.

The Serb, seeking a fourth Madrid Open title, was beaten 6-3 6-4 by Italian Matteo Arnaldi.

Djokovic made his Madrid debut in 2006 and won the tournament in 2011, 2016 and 2019.

However, he said does not yet know if he will play again in Madrid following Saturday's loss to a player ranked 44 in the world.

When asked if it was his final match there, he said: "I'm not sure if I will come back. So, I don't know.

"I mean, I'll come back, maybe not as a player. I hope it's not, but it could be."

Djokovic said his "level of tennis is not where I would like it to be", and added: "I lost to a better player.

"I've had a few of these this year where I lose in the first round, unfortunately."

It was a third consecutive defeat for the 24-time Grand Slam winner, who is seeking a 100th career title.

He also lost in his opening match in Monte Carlo this month, after being beaten in the Miami Masters final in March.

"[It's a] kind of new reality for me, I have to say," he said.

"You know, trying to win a match or two, not really thinking about getting far in the tournament.

"It's a completely different feeling from what I had in 20-plus years of professional tennis, so it's kind of a challenge for me mentally to really face these kind of sensations on the court, going out early now regularly in the tournaments.

"But that's, I guess, the circle of life and the career. Eventually it was going to happen."

Arnaldi just happy to play 'idol' Djokovic

It was a second career win against a top-five player for Arnaldi, 24, who was facing the Serbian fourth seed for the first time.

"He's my idol, he's always been, so I was just glad that I could play him," Arnaldi said.

"To play him on a stage like this was already a victory for me.

"But he's not at his best right now so I came on court to try to play my best tennis and win and it happened, so right now I don't even know what to say."

Three-time champion Djokovic, 37, made 32 unforced errors against an opponent who brought a series of delightful shots out of the bag throughout.

Also progressing to the next round with Arnaldi are British trio Cameron Norrie, Jacob Fearnley and Jack Draper.

British number three Norrie, who is recovering from illness, started slowly against Czech Jiri Lehecka before winning 2-6 6-4 6-0.

Fearnley, the British number two, similarly lost his first set before overcoming another Czech in top-20 seed Tomas Machac, booking his passage to the next round with a 1-6 6-3 6-2 victory.

Then world number six Draper put in a dominant peformance against Dutchman Tallon Griekspoor, winning 6-3 6-4 to set up a match with Italy's Matteo Berrettini in the next round.