The reigning world champion, sixth in the dry Saturday Sprint, spent the opening half of the wet grand prix sandwiched between Alex Marquez and Franco Morbidelli for third.

The Italian then wrestled second from the Gresini machine of Marquez, where he looked set to finish, with VR46’s Marco Bezzecchi having already escaped into the distance.

But it all came undone just a few laps later when Bagnaia lost the front of his Desmosedici through the final sequence of right-handers.

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“I crashed. I'm very upset, sincerely. I had this kind of crash that you don't understand,” he said. “Sometimes you crash and you don't know why, and these are the most difficult to understand, the most difficult to learn from.

“In those 16 laps I did the same manoeuvre but in this lap I crashed. It's also not a normal crash, because normally when you lose the front, it's because you braked too much or you released the brakes too early.

“Today I lost the front touching the gas. So it's something that is more difficult to understand. But that's it. I did a mistake.

“I was wondering that this year I was a better rider, more precise, without mistakes, doing better things, but the second race of the year and I already crashed.

"So it's something that makes me very angry.”

The incident sounded similar to some of the ‘pressure off’ accidents that Bagnaia suffered in the opening half of last season, after which he fought back from 91 points down to win the world title.

“I was feeling really great. Without forcing, without doing crazy things, I was second. I was already sure that Marco in front was too fast for me, I was already with 5 seconds of gap,” he said.

“I was just controlling the [gap] with Alex. And that's it. But it's for that reason that I'm more upset. Because normally when you control, you don't have to crash like this, and this is something that I have to understand.”

The double Portimao winner re-joined the race but finished 16th and last, costing him the title lead to VR46 Academy colleague Bezzecchi by 9 points.

“I'm happy for Marco, I think he really deserved the victory. He was unbeatable this weekend,” Bagnaia said. “He was very competitive yesterday, very competitive today in the wet.

“So his first win in Moto3 was here, his first win in MotoGP is here, so he can be very proud of himself, and I'm confident that he will be very competitive all of the season.”

Bagnaia's factory Ducati team-mate Enea Bastianini missed the event due to his fractured shoulder in the Portimao Sprint.