Dani Pedrosa says his chances of winning the MotoGP title "are not over" despite falling 38 points behind leader Jorge Lorenzo.
Pedrosa was due to start the San Marino Grand Prix from pole position but had a problem with his bike on the grid.
He eventually started from last place but crashed out on the opening lap when he was hit by Hector Barbera.
He said: "Now the championship is obviously more uphill for me, but I will continue. It's not over for me."
The original start was aborted when Karel Abraham stalled his Ducati on the grid.
That led to a delay, during which Pedrosa had a problem with the front wheel of his bike and was forced to start from last place.
"It was total chaos at the start. It all began with the restart because the procedure was not at all clear," he said.
"Nobody knew if it was one minute until the start, three minutes - we were also getting different information about the number of laps we would race, 26 or 27.
"Then suddenly we were told it was one minute to the start of the race, with no board signage, nothing.
"The mechanics were rushing to prepare and when they tried to take off the tyre warmers my front wheel was somehow locked. They tried to unlock it but they weren't able to and they put me to the back of the grid.
"I tried to remain focused, not make any mistakes on the first lap, make clear moves to overtake riders and I was eighth or ninth by the sixth corner when Barbera hit me from behind, and that was it."
Barbera - who has had a season littered with crashes that have seen him break a leg and injure his back - did apologise to his compatriot.
He said: "I took out Dani and that was the last thing that I wanted to happen.
"It was my fault that he crashed out and I apologise profusely to him for that."
Lorenzo was left with an untroubled run to his sixth win of the season, and a result that almost trebled his championship lead.
"I'm very upset because even though it's easy to say now, I think I could have had a chance to win this race, even starting from the last place on the grid," Pedrosa added.
There are five races left in this season's championship, with the next race at Aragon in Spain on 30 September.