Rossi - Poor Quali at Argentina GP
Some riders tried changing slicks, although only pole sitter Jack Miller could make them work and the factory M1 duo were among the majority to stay on wet tyres throughout.
"Today was difficult. We always suffer in the wet and at the moment we are not on the same level as our main rivals. We have to keep working on the bike's set-up and keep improving in the wet," Vinales said.
"We have work to do during this season to be strong… We'll hope for a dry race, that would suit us much better."
Rossi explained that he found the wet tyres too soft on the drying track and was soon 'in crisis'.
"It was a difficult day for me, because in these conditions - when you have to go out on the wet tyre, but the asphalt is becoming dry - I'm in a lot of trouble," he said.
"Because for me the tyres are too soft and after two laps I got a lot of crisis, especially with the front but also the rear.
"I can't push, because every time I try to push more I feel the front close.
"At the end of the qualifying I tried to do a smooth lap, I was able to improve my time, but anyway it was not enough to be with the top guys.
"We have to work, but especially we have to hope that tomorrow will be full dry or full wet, because then I feel quite comfortable, but in these half-and-half conditions it will be very difficult.
"My preference is full dry, for sure, because for me with the full dry I have a good pace to make a good race.
Vinales and Rossi had been sixth and seventh fastest in the dry Friday practice, then tenth (Rossi) and 17th (Vinales) in the fully wet FP4.
"We expect tomorrow to be dry but, regardless of the weather, it will be a hard race. We aim to make another step in the warm-up tomorrow morning," said team manager Massimo Meregalli.