Marc Marquez could not breathe for five seconds after his enormous crash in practice at the Thailand Grand Prix.
During an out lap towards the end of FP1 on Friday, the five-time world champion launched into a highside and hit the ground heavily at turn seven, with his bike totally wrecked from multiple rolls.
Following an initial examination at Chang International Circuit, Marquez visited Buriram Hospital for checks and an MRI, with Repsol Honda team boss Alberto Puig describing his rider as "lucky" to escape with contusions on his leg, back and hip.
Marquez is due to undergo further treatment but tweeted to say he was "fine" before returning to the track to take part in FP2, where he finished sixth.
He will be crowned 2019 champion on Sunday if he gets two more points than Ducati rival Andrea Dovizioso and spoke to reporters after the two sessions to describe the scary start to his race weekend.
"It was around five seconds that I couldn't breathe," Marquez told reporters.
"For that reason I was there on the floor, on the gravel. It is only five seconds but for me it felt like it was like 20 seconds.
"It was a big impact and it is true that step by step, [I got] better and better and when I arrived in the medical centre, I was already okay.
"But then, I fully understand, the doctors try to manage the situation in the best way and they prepare to have a deep scan about all these things. We went to the hospital.
"The most important thing is that I am okay – painful everywhere - but the biggest thing after the crash was that I couldn't breathe in a good way. This was the main problem."
Explaining the crash, Marquez added: "I was much slower than the normal laps because I was [coming] out of the box. It was new tyres, maybe the track was not clean enough but it is normal.
"I locked the rear. It's not a mechanical problem, more my mistake because I was riding slow or maybe the tyre was not ready or a little bit on the dirty place [of the track]. Difficult to understand."
With rain forecast for Saturday, FP1 and FP2 took on an added importance in the battle to be one of the 10 riders to go straight through to Q2.
Yamaha riders were dominant in Buriram, claiming four of the top five positions with Fabio Quartararo just under two tenths clear of Maverick Vinales at the top of the standings.
Franco Morbidelli, Jack Miller and Valentino Rossi completed the top five, with Dovizioso coming eighth and his team-mate Danilo Petrucci looking vulnerable in 11th.