Fabio Quartararo says an "out of control" front tyre pressure after three laps of the MotoGP Aragon Grand Prix led to his career-worst 18th-place finish and ceding the championship lead.
The Petronas SRT rider ran in second in the early stages of Sunday's race having started from pole, but quickly dropped down the order.
Quartararo ended up 21.5 seconds off the lead down in 18th and out of the points, which lost him the championship lead to Suzuki's Joan Mir - who was third - by six points.
The Frenchman explained an issue with his front tyre led to an increase in tyre pressure after just three laps, but is unsure what caused the problem and defends his decision to run with the medium front.
"[He's] really struggling because we were there in good shape to fight for a great result, but we need to find out why the front pressure went totally out of control, out of the normal," he explained.
"It really felt strange because we had the pace to fight, I would not say for the win or the podium, but the top five, six.
"Would have been great, but the front tyre went out of control and we don't know why.
"For me, the choice was correct because the first three laps were perfect.
"I had a great feeling and everything was OK, but the problem was from lap three we already had the pressure much higher than normal.
"And you can imagine with 20 laps remaining in the middle of the race how high the pressure was, it was totally out of control and we've never rode in this condition.
"We couldn't brake, couldn't turn, couldn't lean the bike - so that's the reason why I was going so wide and couldn't stop the bike."
Quartararo suffered two heavy crashes in practice and injured his hip, but says his physical condition gave him no issues in the race.
Suzuki's Alex Rins won the race, with Quartararo's title rival Mir third to take the lead in the standings for the first time.
With a second race coming up at Aragon next week, Quartararo admits he might struggle to match Suzuki in the Teruel GP but is not worried about the manufacturer's threat in the final rounds.
"Looks like the Suzuki is really fast," he said, when asked by Autosport if the Suzukis will be harder to beat now.
"I think we can fight with them. Maybe in Aragon it's difficult, but then we'll arrive to tracks like Valencia where normally we are fast.
"In the November test with the new tyres we were going so fast there and I think we can fight with them, but we need to be really clever.
"The next race will be important to not lose any points and try to win points, which for me is so important.
"But I feel we can fight with them. In the end, it's only six points [to Mir] at the moment and we can fight for a great result."