Movistar Yamaha rider Jorge Lorenzo admits he feared he had suffered a serious injury after being taken out of the Catalan Grand Prix by Andrea Iannone on Sunday.
Lorenzo started brightly in Barcelona, taking the lead in the opening laps after starting from second on the grid, but the Spaniard dropped down to fifth after struggling with front-tyre wear.
While it appeared he would still maintain his MotoGP riders' championship lead, Lorenzo was taken out by Iannone at turn 10 midway through the race.
The Ducati rider went into the corner with too much speed and, despite his best efforts, could not stop in time to avoid hitting Lorenzo from behind.
Lorenzo's retirement meant he dropped down to second in the championship standings, 10 points behind Honda's Marc Marquez, who finished second behind race-winner Valentino Rossi.
And Lorenzo revealed after the race he thought he had suffered an injury following Iannone's hit.
"I don't know if he braked too late, or didn't brake knowing someone was in front of him, and finally I feel a big impact and I was lying on the ground," the 29-year-old said.
"First I was scared I had broken my hip or my collarbone, but after a minute I saw it was only the [shock of the] impact."
The three-time world champion added: "You can make a mistake, but you have to go and say 'sorry' and 'it was my fault'. Instead of that, he just asked me 'what happened to your bike?'
"That was the worst [thing] for me, he didn't say sorry and he didn't understand it was his mistake. He is making too many mistakes that put other riders at risk.
"Dani [Pedrosa] made a mistake at Austin, but [at least] he apologised to [Andrea] Dovizioso."
Iannone, who will make way for Lorenzo at Ducati in 2017, was penalised for the collision and will start the next race at Assen on June 26 from the back of the grid.