Valentino Rossi says he needs to be able to ride in the dry on Saturday to be completely sure of being able to take part in Sunday's Aragon Grand Prix.
The Italian rode a MotoGP bike for the first time since breaking his right leg 22 days ago in a motocross crash in Friday's free practice sessions, both of which were held in damp conditions.
Rossi ended the day down in 20th place, 2.059 seconds slower than pacesetter Dani Pedrosa.
Speaking afterwards, Rossi said he didn't "feel a lot of pain" in his leg during practice, and that there had been no swelling, but admitted that the wet track had made his life a lot easier.
Asked if he could be sure of racing on Sunday, he admitted he needed to test himself in dry conditions before being fully certain.
"With the conditions of today, if it’s wet, I don’t have particular problems," Rossi said. "For sure the dry is a lot more demanding.
"I have to ride a bit more, [in the dry it's] more effort on the arms, the shoulders, because in braking I don’t have the power of the leg to brake the bike.
"The other thing is on the dry you have to move on the bike more from one side to the other, and also when you are at full lean you are more outside [the bike].
"This I don’t understand with the R1 [road bike that he tested at Misano earlier in the week], because the R1 is more normal, like the M1 on the wet. But the M1 in the dry you have to stay more outside.
"So with these conditions, no problem, but for the dry we need to wait tomorrow, hoping for good conditions."
Van der Mark set for test
Yamaha had placed World Superbike rider Michael van der Mark on standby for the Aragon weekend in case Rossi was unable to ride.
But, with van der Mark looking likely to miss out on what had been set to be his MotoGP debut, the Dutchman revealed he is set for a test on the Yamaha M1 at some point in the future.
"Looks like he [Rossi] is fit, he's looking good, he has no pain, so this is really positive for him," van der Mark told Motorsport.com when asked whether he expected to ride on Saturday.
"I spoke with Yamaha, and I will be testing a bike soon, so even though I'm not riding, I will get a nice test.
"They just want to give me this opportunity, they just want to let me ride a GP bike, which is quite good."