A first MotoGP riders' title since 2015 courtesy of new signing Fabio Quartararo, but also a shock mid-season split from Maverick Vinales, resulting rider reshuffle and the final chapter of Valentino Rossi's legendary career.

It's little wonder that Yamaha Racing managing director Lin Jarvis describes 2021 as "a bit of a weird year for us."

Everything began so perfectly, with Vinales and Quartararo winning the opening three races in a row. But cracks were already starting to appear with Vinales' results dropping from 1st to 5th to 11th.

While Quartararo continued to rack up podiums and wins, Vinales wallowed at the lower end of the top ten. Fifth place at Catalunya, proved a false dawn, and the Spaniard hit rock bottom with last at the Sachsenring, before a glum podium return at Assen.

The Dutch event also saw reigning title runner-up Morbidelli, who had taken just a single podium on the outdated 2019 bike, withdraw for major knee surgery, while team-mate Rossi failed to make an impact on the Factory-spec Petronas machine.

"To sum it up, I think we were one up - three down," Jarvis said of his riders' fortunes.

"With Vinales and Fabio at the factory team and Valentino at the satellite team with Frankie [Morbidelli] it was a great package of riders.

"The season started incredibly strongly, certainly for the factory team, because we won the first three races. We were on a roll, on a mission, we'd corrected our [bike] problems of last year and could see that this could be a good championship.

"Fabio's championship continued to evolve in a very positive way. In the races where he struggled, he didn't lose everything. He always managed to gain points. He won five races. So I think everyone would agree Fabio clearly deserved to be champion.

"On the other side, obviously we had problems because Maverick was inconsistent throughout the year, then we reached a crisis point basically in Assen, where he requested to leave.

"He was not happy, he wanted to leave and move on. We agreed and then had two options; either stop now or continue and finish until the end of the season in a professional way."

The latter option was agreed but, to put it mildly, didn't work out as planned.

"What happened after the summer break took us by surprise, I have to say! But that resulted in Maverick leaving the team [immediately]," Jarvis said, referring to Vinales being suspended from the second Austrian round after deliberately over-revving his engine in frustration during the opening Spielberg event.

While Johann Zarco split from the factory KTM team midway through 2019, the Frenchman hadn’t finished higher than tenth place and his team-mates no better than sixth.

In Vinales' case, he was walking away from a highly paid contract on a bike with which he won the opening race and finished second (from pole position) at Assen, and a team that was leading the world championship with Quartararo.

"Some things happen and evolve that you wouldn't have expected," Jarvis said with a fair degree of understatement.

"When Maverick renewed with us for two years [2021 and 2022] and Valentino was departing, arguably I would say we had the strongest team on the grid to start this year.

"Maverick was in his fifth year with us and should normally step-up to be the leader of the team. Because prior to that, Valentino had always been there, with so much history and connection in Yamaha that can sometimes cast a shadow over the team-mate.

"Maverick started really well. So if you'd asked me in Qatar, I'd have said I'm totally convinced we made the right decision [to renewal]. But who could imagine from winning the first race you would end up in the ninth race in a crisis where the rider chooses to leave the company, at the same time we were finishing 1-2 in Assen?

"You could hardly say the bike was uncompetitive or that the team was not performant! And finally, we won the world championship.

"But some things catch you by surprise. It was difficult to deal with at the time because it was completely unprecedented. That said. I think we all managed it in the best way possible finally."

While Quartararo kept control of the riders' title, Vinales' exit dealt a blow to Yamaha's constructors' and especially teams' championship challenge. Morbidelli, still injured, was hired to fill the void, with test rider Cal Crutchlow drafted in until the Italian was fit to return.

Ultimately, Morbidelli could only contribute a handful of points and Yamaha were beaten by Ducati in both the constructors' and teams' standings.

"Maverick leaving put us in difficulty certainly for the teams' championship. Because you need two riders to score points, So that was a big problem. That then became an opportunity for us to bring Franco into the factory team when he was recovering from injury," Jarvis said.

"But, Franco's season was also not what we expected, not what he wanted. Last year he was second, he rode a great season, took Joan Mir right to the end of the championship and did very well, won three races.

"This year, due to Covid, he started on the 2019 spec bike, because that decision was taken in the middle of last year. So he started with a technical deficit because the '19 bike really did stay pretty much where it was, whereas the 2020 spec bikes were upgraded [for 2021].

"I think the level of all the factory bikes were raised, which put Frankie in difficultly at the beginning of the year. Then of course he got his injury mid-season and decided to bite the bullet and take the operation to get his knee fixed, which I think was definitely a smart move.

"So after Maverick's sudden, unexpected departure and then considering the rest of the year we took the decision to bring Frankie in. Basically we upgraded him 1.5 years ahead of schedule. Because if Maverick had stayed, Maverick would have been in the factory team to the end of 2022.

"So we upgraded Frankie in the hope that he could fight for the teams' points for the rest of the year, but it's not easy. He came back early from that quite serious knee operation. It's great for him for next year [to do five races with the factory team], but it hasn't brought a lot to the team for this year in terms of pure points - but we still totally believe it was the right decision.

"I think having Fabio and Frankie is a pretty good team next year, so we are happy about that."

The only Yamaha rider other than Quartararo to complete a full season was Rossi, switching to the satellite Petronas squad for his 26th and final grand prix campaign.

"Obviously Valentino wanted to start this year with the energy and effort to try again. Because [the 2020 season] was Covid, it was weird, we started in July, we had 14 races, there were no spectators. Many thing going on," Jarvis said.

"So Valentino really wanted to try to do a full season and to see if he could still be competitive. But in the early stage of the season it was clear the level had been raised again, all the young riders were getting faster and faster. Fabio was incredibly fast, Maverick won the first race. So it was never easy for him from the beginning of the year."

Rossi had taken a best result of tenth place when he announced his decision to retire during the summer break, later adding an eighth place in the rain-interrupted Austrian round on his way to just 18th in the world championship.

"I'm sure he would be the first to admit the season finally was disappointing for him in terms of pure results. But I still think his year was totally valid and even with hindsight I think we'd still do the same again because I think he needed to do this extra year," Jarvis said.

"So we finally had one up and three down, but now we have Dovi joining us."

Andrea Dovizioso, a Tech3 Yamaha rider back in 2012 and then triple title runner-up at Ducati, was picked to take over from Morbidelli at SRT for the closing races of 2021 ahead of a full 2022 season.

"It's a new opportunity for Dovi to return to the sport which I think is great for him," said Jarvis. "Dovi has been second in the championship multiple times in recent years, he started on the old bike, let's call it the slow bike, but ]now] he'll be on a 2022 spec bike. The experience he's got [on the A Spec] will put him in a better place.

"So I'm really happy with next season's line-up as well, but [2021] has been a bit of a weird year for us."

Rookie Darryn Binder complete's Yamaha's 2022 line-up, riding an A-Spec bike alongside Dovizioso at the revised RNF team. At present, Morbidelli is the only Yamaha rider with a MotoGP contract in place for 2023.

Meanhile Vinales, having joined Aprilia for the closing stages of last season, will remain on the RS-GP this year.