The Norwegian stopped early in the monster 47.70km test from Kineta to Pissia and was close to tears when he reached the finish after replacing the wheel and losing more than three minutes.
Having regained his composure when he returned to the Loutraki service park, Ostberg admitted he would need to view the onboard footage in a bid to understand what happened.
“At the beginning of the stage we did a lot of switching between concrete and gravel and each time the surface changed we went over a step,” he explained. “I was going through a corner and onto a step when the wheel just fell off.
“There was no damage to the suspension or the steering. The only thing left on the hub was the bolt, the nuts and the cone where the wheel fits. Maybe it happened that I again hit something in the absolute worst possible angle with the tyre, I don’t know,” he added.
Ostberg said personnel from the Qatar M-Sport team had gone into the stage to try to find the wheel so they could investigate further with the help of onboard footage.
“It seems like things are on the wrong side of the limit at the moment. It happened at a tight hairpin left, a first gear corner and nothing can be massive at that speed. I don’t know what to say.
“On all the rallies we have retired lately we were able to get back into speed, and I will try to do the same here. We will try to reset for tomorrow,” added Ostberg.