Jorge Lorenzo says he reverted to Ducati's 2017 MotoGP bike on the final day of testing at Buriram because he was struggling for confidence with the manufacturer's '18 challenger.
Lorenzo finished no higher than 10th on the first two days at Buriram, but was even further down the testing times on Sunday after running on old tyres and wound up 22nd.
He decided to revert to Ducati's GP17 for the final few hours of Sunday's test, but said afterwards he believes the new bike, which he said on Saturday he still did not feel "comfortable" with, remains the better bet.
"Today has been difficult, [I had] not so much confidence, and I was very far from the first riders," said Lorenzo.
"That's why we decided to try again the old bike.
"It was important to try the old bike again - it still has some points that are better than the new one, also some points that are worse.
"[But] if I had to choose at this moment and make a conclusion, I would choose the new bike. We have a bigger potential [with it]."
When asked to specify what he was struggling with on the new bike, Lorenzo replied: "The new ['18] chassis still has negative points that I don't like so much."
