After his debut MotoGP victory at Misano, Franco Morbidelli began thinking "that maybe I could have fought for something bigger" in terms of the world championship.

But the Petronas star, the only Yamaha rider without a Factory-spec bike this year, feels he will need to reset his expectations after witnessing the top speed difference in Sunday's Catalunya race.

"After seeing my potential in a straight-line here being even less than the other Yamahas, I need to step back, try to relax, enjoy every lap, every race and not think about anything else," he said.

"Just do my job without thinking about anything special in the championship because, as I already said, Factory riders need to think about the championship, but I realised this even more in this track with such a long straight."

While all the Yamahas are suffering in a straight line this season, Morbidelli was tied with Aprilia's Bradley Smith for the slowest top speed during the race at 337.5km/h.

Monster Yamaha riders Valentino Rossi and Maverick Vinales were only 1km/h quicker, with Morbidelli's race-winning team-mate Fabio Quartararo the fastest M1 at 343.9km/h, albeit some way off Francesco Bagnaia's 351.7km/h for Pramac Ducati.

But those one-off peak speeds are more influenced by slipstreaming, and an average of each rider's top five speeds is more representative.

In that respect, Morbidelli's average was a 335.3km/h, the slowest of anyone, with Vinales on 337.0km/h, Rossi 338.5km/h and Quartararo 339.1km/h.

The other statistic that stood out for Morbidelli was during the closing stages of the race when his top speed was between 329-335km/h. But over those same laps, Bagnaia was clocking 347-352km/h!

"This weekend I was 6 km/h slower than the other Yamahas, and at the end of the race I was 22 km/h slower than the Ducati," Morbidelli said.

That speed difference also has a major impact on the Italian's tyre preservation.

"You can manage the tyre when you have power in a straight line, and I'm clearly the weakest in the field from this point of view," he explained.

"I just had to start, make the maximum, and couldn't make any strategy. I couldn't manage the tyres because I just wanted to give the maximum when I had the tyre, and finally I destroyed everything.

"But I sill think it was the best strategy to do for me and for my package."

Morbidelli ultimately dropped from pole position to fourth place in Sunday's race, but that still beat his best result prior to this season and – despite two DNFs and a 15th place - he's fifth in the world championship.

"We clearly improved compared to last year. I am clearly a better athlete, more professional and I'm more serious on track. I work better with the crew and this affects a lot our results," said the Italian.

"Actually our results are very good. I am very happy about how we are doing. We've been very unlucky and we are still fifth in the world championship. This is amazing."

Morbidelli is 31 points behind team-mate and world championship leader Fabio Quartararo, who has the same Factory-spec machinery as the official Yamaha team.