Bagnaia had qualified second behind championship leader Jorge Martin, but was down to 14th by the end of lap 1 following a dreadful start on his GP24.
Lacking the speed to mount any sort of recovery, the Italian then ran wide over the gravel at the exit of Turn 7 on the third lap, rejoining the track at the rear of the field.
With it clear by then that the problem he was suffering was significant, the reigning champion returned to the Ducati garage to retire from a race for the third time in 2024.
Bagnaia’s troubles followed a late crash in qualifying on Saturday morning, which forced him to switch to his second motorcycle for the 13-lap sprint.
But the Borgo Panigale marque still doesn’t understand what exactly went wrong with his spare bike, with work expected to continue overnight ahead of Sunday’s full-distance race at Le Mans.
“As soon as I started on the sighting lap I felt something strange and then in the warm-up lap I went wide in corner seven already in a strange way,” Bagnaia said.
“And [when I] started [the race], the bike had a really huge wheelie. Then it was very difficult to do more or less everything. I lost the front in corner six before going wide in corner seven, almost in acceleration, so something [was] wrong.
“I feel it was not working in the way I expect it to and it’s something that can happen.
“For tomorrow we will try to solve everything, but here we had to change the bike from the crash of this morning and the other way maybe was to re-adapt a bit.
“But my team is already checking everything. It's not easy to understand when these kinds of things happen, but my team is so good and we will solve everything.”
Bagnaia said he was left with no option but to return to the pitlane, as it was no longer safe to continue the race.
“I retired because something was not... it was dangerous,” he admitted. “I'm not the guy that wants to retire. Also to have any new information for tomorrow it was better to continue, but it was better to stop.”
With Bagnaia dropping out of contention early, Pramac rider Martin faced no real threat as he romped to his third sprint win of 2024 and cement his status as the early championship favourite.
Bagnaia, in turn, now faces a 29-point deficit to Martin in the riders’ standings, having also retired from a crash-filled sprint at Jerez a fortnight ago.
The 27-year-old says the troubles he faced on Saturday afternoon at Le Mans can be traced down to his incident in qualifying, as he urged the need to score points on a regular basis to boost his chances of winning a third title.
“It's true that we have to find consistency, but it's two weekends in a row that on Saturday that we had to face some bad luck,” he added.
“It's bad luck that it comes from my mistakes of the morning because without this crash I was having the same bike and everything was good.
“We were not expecting a reaction like this for the sprint.”
