Valentino Rossi fears a Saturday washout could hinder Ducati's chances of a strong result this weekend in the Aragon Grand Prix.
Rain has typically been a leveller for Ducati, with two of Rossi's three podiums for the Italian outfit coming in the wet.
His only dry rostrum came last in the preceding grand prix at Misano.
With dry weather forecast for Sunday however, Rossi fears a Saturday washout could end up hurting Ducati by forcing it to guess on dry set-up - an issue exacerbated by the fact Honda and Yamaha's works squads have data from their recent Aragon test to fall back on.
"If tomorrow is similar we can be faster and start from a better position, but unfortunately for us it is [also] a bit of a disadvantage if the conditions remain bad tomorrow because for sure if Sunday is dry the other guys already have the setting," Rossi said.
"We can do nothing but take it practice by practice, make the best we can and wait for the forecast and try to do the maximum.
"I hope that if we work on the wet and make the normal modifications for the dry it [will be] a good setting, but we have to wait. Our target is to make a better position for tomorrow if it is wet."
Rossi added that his eighth place finish in second practice – compared to fourth for team-mate Nicky Hayden – came after a gearbox setback.
"So, we have some problems this afternoon in the wet session, because I had a gearbox problem on one bike," he said.
"We had to stop and prepare the other bike for the wet conditions. On the last lap I lost some time, so I think under the rain we can be faster than today, closer to the top guys."
Hayden meanwhile said the rain had blurred his impression of Ducati's new chassis, although he was able to identify areas in which he says Ducati still needs to improve in the wet.
"It was wet in the afternoon, but I didn't enjoy riding in the rain as much as I usually do - I was missing some rear grip on corner entry and at the first touch of the throttle," he said. "We've got to improve that.
"I only rode with the new chassis today, but with the rain, I'm not really able to give an impression.
"They're calling for more rain tomorrow, so we might have to manage the rain tyres. When it dries, this track can chew them up quickly, so we might need to make sure we save enough for qualifying. We'll see what tomorrow brings."