Qatar MotoGP: Yamaha's Jorge Lorenzo says helmet issue cost him win

The race was eventually won by Lorenzo's Yamaha team-mate Valentino Rossi.

But for most of the distance Lorenzo had been the team's main victory threat, as he battled with the Ducati of Andrea Dovizioso and led 15 of the 22 laps.

Lorenzo lost pace in the closing stages and fell back to fourth behind Andrea Iannone on the second Ducati, and said that slump was because a helmet issue left him struggling to see.

"I was feeling better and better, but suddenly there was something wrong when in the top part of the helmet the foam came loose and came down so I lost half of my vision," he explained.

"I couldn't see the corners very well and couldn't concentrate or ride like before and I was losing half a second or more per lap.

"In a race where, at minimum, I could fight for the win, I finished fourth."

Prior to the helmet problem, Lorenzo said there had been areas where his Yamaha was struggling to match the much improved Ducati, but that he still felt capable of overcoming Dovizioso for the race win.

"I was faster and I passed him where I could in the fast corners," he said.

"On the [top] speed and in braking the Ducati was much stronger than our bike, but we could recover on corner speed while the acceleration was similar.

"To be honest, I thought that I could win the race, though it surely wasn't going to be easy, because Valentino had a very strong pace at the end of the race."