Valentino Rossi has tipped Maverick Vinales to be a threat in Sunday's Qatar MotoGP after being impressed with the young Spaniard during FP1.

Rossi posted the second fastest time on the Movistar Yamaha with a lap in 1m 55.707s, which left him two tenths behind Yamaha team-mate Jorge Lorenzo.

The nine-time world champion followed Suzuki prospect Vinales in the opening free practice session and praised the 21-year-old afterwards, touting him as a future MotoGP winner.

"Maverick rides very well, he has very good lines and a very good way to use MotoGP and I think he will be one of the riders that can win in MotoGP," Rossi said.

"He is a great talent, he is f*****g young - too young! And also the bike, the Suzuki is improved. So I think that Maverick can stay with us in the race, yes."

Rossi also expects the straight-line speed of the Ducati riders to pose significant problems in Sunday's night race, with the long straight at the Losail International Circuit offering the perfect passing opportunity for the super-fast Desmosedici.

Andrea Iannone was third quickest in practice, riding the latest GP16.

"We have some data and it looks like the problem for everybody is this track because the GP16 has 10kph more," said Rossi.

"I don't see the official data but this is a problem and if they are able to stay behind, in the straight they win the race. At the same time, it looks like the Honda is a little bit closer to us and Suzuki improve.

"So I think here in Qatar, top speed will be an important issue for the race. For me, our bike is still better in the corner [than Ducati], so this is better for the tyres. We speak, but nobody knows until Sunday night," he added.

"Apart from that, it was a good start like I said, also because I was able to improve my lap time from the test."

Rossi now feels that MotoGP's new Michelin tyres could work more in his favour this season, compared to the Bridgestones, although he says the theory needs to be proven in a race situation.

"On paper, I think with Michelin it can be a little bit better for me because they are different tyres and also you can arrive a little bit more step by step. For me the tyres and electronics is good for the show, but we have to wait," he said.

"But this is on paper and in the test I finished fifth here and sixth in Australia, so I was not in pole position. My target, if I want to try to fight for the important positions, is that I need to improve in the qualifying, so we have to work from this point of view. I say maybe yes, but we have to wait to Saturday.

"I feel good with the bike but now it will be very important to make a good job because I think today the track is different, a lot more dirt compared to the test, so we need to improve the setting practice by practice to arrive ready for the Sunday," he added.

"Also it will be important to make the right decision for the tyre because it is new and with Bridgestone we had a lot more experience. With Michelin, making the right choice will be important."