Just one lap after Alex Rins had fallen from second place, MotoGP world championship leader Johann Zarco saw his podium chances disappear into the Portimao gravel trap.

But while the Suzuki rider was at a loss to understand why he had lost the front of his GSX-RR, as he shadowed race leader Fabio Quartararo, Zarco did at least get a clearer answer for his own downfall.

Pramac Ducati data showed Zarco had downshifted to first gear instead of second, possibly due to a technical glitch, with the resulting extra engine braking then overloading the front tyre.

"I bit disappointed for sure. Always easier to say it would be better to have a few points than a crash," said Zarco, leader of the opening laps and in third place, sandwiched between Francesco Bagnaia (Ducati) and Joan Mir (Suzuki), while he fell with five laps to go.

"I thought I did a little mistake when I crashed because I did a mistake on the shift down, but then I got also a little issue with the gearbox in that moment. That's why I got not the right gear.

"I just got first gear instead of second gear. Then, while braking with a lot of lean, I got a bit more engine brake and also because the front tyre was not pretty nice on the right side, it didn't support this and immediately I was down.

"So that helped me not be too disappointed, to understand better why I crashed, and also I had to use a lot of energy to keep the pace today because of the front tyre.

"I've been pushing a lot and I think some tenths were missing today. I was not comfortable everywhere, so then you have to give a bit more energy to compensate and the race becomes more difficult.

"But even in that way, I was there, hoping to fight for the podium. That's positive.

"Always the advantage on the straight is pretty important and I saw I could do a huge difference. I was enjoying using it! Then it was pretty good to see how Mir is riding after Rins and Fabio went away."

With fellow Frenchman Fabio Quartararo winning the race, Zarco would have lost the title lead even if he had stayed on track and taken his third second-place finish in a row (which eventually went to Bagnaia).

Instead, Zarco will go to Jerez having slipped to fourth in the standings, 21 points behind the Monster Yamaha of Quartararo.