MotoGP world champion Marc Marquez admits the nature of the Qatar circuit means he is struggling with his injured right shoulder more than he was at the Sepang test.
The Honda rider underwent surgery on a partially dislocated right shoulder - which he sustained in a heavy crash at the Malaysian Grand Prix last year - in November and rode at the recent Sepang pre-season test below full fitness.
Marquez completed 42 laps on the first day of the Qatar test on Saturday and was just 0.361 seconds off the pace in sixth.
But he admits his physical condition hasn't changed much from Sepang - owing to a damaged nerve - and the numerous long right-hand corners at Losail are "stressing" his shoulder "a lot".
"Today we started here in a good way more or less, but it's true that in this circuit I'm struggling a bit more than in Malaysia," he said.
"In Malaysia it was a different riding style, and here with the long right corners I'm struggling a little bit more."
When asked if there was a noticeable change in his physical condition, he added: "I mean... no.
"I would like to say yes, but honestly speaking I have one nerve damaged and [for] one nerve [to heal] in two weeks is no difference.
"It's true that the other part of the body is stronger and the other muscles, I tried to work very hard to be stronger and have more power.
"It's true that I arrive in a better way of physical condition, but at this circuit, I'm struggling a little bit more because these long right corners are stressing a lot the shoulder."
LCR's Cal Crutchlow said at Sepang that the new Honda is worse at turning than last year's bike, with Marquez admitting in Malaysia he was more worried about the bike than his physical condition.
Marquez says Losail tends to show "all of the weak points of the bike", but noted that the situation was similar with the bike at this test last year and he went on to just miss out on victory in the race two weeks later.
"Of course, if you have an easier bike to turn it will be easier for the physical condition," Marquez said when asked if the bike was causing his shoulder problems too.
"We know that Honda is one of the bikes that is more demanding on physical condition.
"Here in this circuit we are one more year [where we are showing] all the weak points of the bike and the riding style; all these long corners are our weak points.
"But last year we started more or less in a similar situation and step by step we got closer and closer [to the frontrunners].
"So, this is the way: try to work, try to find a special set-up here in Qatar and try to be closer to the top guys."
Alex Marquez: Twin crashes rookie error
Marquez's younger brother and team-mate Alex suffered two crashes on Saturday in Qatar, and ended up a distant 21st as a result.
Commenting on the tumbles, Alex says they were simply his own mistakes rather than anything to do with the bike and says "crashes will come" as he continues to adapt to the bike in his rookie year.
"Was my mistake [the crash]," he said. "I made a little mistake going in and that's it.
"It's not like I have a problem with the bike.
"So we need to just keep going, keep pushing. The crashes will come, I'm a rookie and I need to find the limit like that."