Double MotoGP champion Jorge Lorenzo apologised to his team and fans after honestly admitting he was simply 'scared' to take big risks during Saturday's Dutch TT.

The Movistar Yamaha rider initially rose from ninth to sixth during the early wet stages of the Assen race, but after pitting for his slick-tyre bike Lorenzo began suffering flashbacks of last year's accident.

Lorenzo suffered a broken collarbone when he was thrown off in wet practice one year ago, making an amazing return from surgery to claim fifth in the race.

While the Spaniard had been comfortable in the fully wet and then fully dry conditions at the end of this year's grand prix, the on-off rain while on slicks during the middle stages saw him drop as low as 17th.

"It has probably been my worst race in MotoGP. The worst finishing positions," began Lorenzo, speaking at Assen on Saturday evening. "The bike worked well in the wet. The bike also worked well in the dry. But I was not confident enough.

"I was just scared at this track. When I saw the rain spitting in some corners I just didn't want to take risks.

"So today has been 100 percent my fault. I was to apologise to the team, the people that work with me and the fans because I was unable to be brave, to be fast in these track conditions like the other riders."

When the rain stopped, Lorenzo regained some of the lost ground but could only finish in 13th place. His best lap was the 25th of the 26.

"It was a pity. In the dry we were competitive, but in these conditions it was my fault. Not being brave and not being competitive. Last year I made something impossible, this year was the opposite. I was the more scared rider.

"When I saw some spitting in some corners on the dry tyres I just didn't want to take the risk to crash again and be injured again at this track. Probably the memory of last year was making me too cautious of the risks and too afraid to be fast.

"Every time I saw the spitting and felt the bike move a bit I got some flashbacks. In the last laps when it stopped spitting my performance was more acceptable, but not before.

"I've won races where you change the bike, but we don't have many races in conditions like this, with rain on slicks. Today I was too scared. You have to admit it, accept it and try to find out why. Luckily these conditions don't happen often."

Following last year's Assen heroics, Lorenzo bent the plate inserted into his shoulder in a big accident next time out in Germany, requiring another round of surgery. The Spaniard then went under the knife again this winter to have the plate removed.

The Assen race was the latest 2014 setback for Lorenzo, who came within four points of winning a third MotoGP title last season but is only fifth in year's championship, with two podiums from eight starts.