Rossi: Marquez has taken 'big step' to 2017 MotoGP title

Marquez's fifth win of the season has given him a lead of 16 points in the championship over Andrea Dovizioso, with whom he was tied prior to the weekend.

The Honda rider has won four of the last six races, finished second at the Red Bull Ring after a final-lap battle and was among the contenders at Silverstone before his engine failed.

Rossi believes his Yamaha team-mate Maverick Vinales and Ducati's Dovizioso, Marquez's main rivals, will struggle to stop him from now on.

"I think the championship now, for the opponents, is very difficult," Rossi said.

"[Marquez's Aragon win is a] very big step.

"Looks like after Brno, the [private Honda] test, they improved the performance a lot.

"Marquez won in Brno, lost the race in the last lap in Austria.

"At Silverstone was very strong but broke the engine, but he won in Misano in the wet and won here."

Rossi's comments follow Vinales' own admission that Yamaha's current competitiveness will make it "impossible" to overhaul Marquez, who is 28 points ahead of Vinales.

There are four rounds remaining in the 2017 season, in Japan, Australia, Malaysia and Valencia - all venues Marquez has won at in the past.

LCR Honda rider Cal Crutchlow echoed Rossi's opinion, having predicted from the outset that nobody would be able to challenge Marquez at Aragon.

Asked by Autosport if he felt Marquez now had one hand on the championship trophy, Crutchlow nodded and said: "He's riding strong. I said he would win here and he did.

"He won at Motegi last year [to seal the championship] when he didn't need to win, so maybe he'll win there again as well."