The 2021 MotoGP season certainly wasn't short of talking points - here are five of the most read storylines on last year:

Quartararo plummets from 1st to 13th after a mystery issue in the Spanish GP

For the first half of the Spanish MotoGP, Fabio Quartararo looked comfortably on course to extend his title lead with a third race win in a row.

But a 1.5s lead over Jack Miller suddenly vanished and a dramatic decline saw the Monster Yamaha rider plunge all the way down to 13th place by the chequered flag.

But what exactly went wrong?

Rather than a tyre issue, Quartararo looked in physical as well as mental pain as he returned to the pits and the young Frenchman later confirmed he had struck arm-pump problems.

The eventual world champion underwent surgery but was back on track, and back on the podium, next time out in front of his home fans at Le Mans.

Quartararo penalised for open leathers, loss of chest protector in Catalunya

After taking his first win since arm-pump surgery in Mugello, Fabio Quartararo's title winning season took another unexpected twist in Catalunya.

After crossing the finish line in third, Quartararo was subsequently hit with two post-race penalties.

The first was for failing to surrender enough time when cutting the chicane, dropping the Yamaha rider from third to fourth place.

The second penalty was then added for the bizarre 'wardrobe malfunction' that saw Quartararo ride with the zip of his leathers open and discard his chest protector in the closing laps.

While many felt he should have been black-flagged for his own safety, Quartararo was instead allowed to finish the race. The second penalty further demoted Quartararo, from fourth to sixth, in the final classification.

The reason for the zip on Quartararo's leathers opening was never established but subsequent analysis by Alpinestars found the suit to be 'in normal working order with all zippers and fasteners fully functioning.'

That added weight to the theory that the zip might not have been not fully closed at the start of the race, or that the chest protector may have moved out of position, prompting Quartararo to react.

Yamaha suspends Vinales for 'Unexplained operation of the motorcycle'

Yamaha continued to make headlines with the shock announcement that it had suspended Maverick Vinales from the Austrian Grand Prix 'due to the unexplained irregular operation of the motorcycle during last weekend's Styria MotoGP race'.

The Yamaha statement explained that the decision to withdraw Vinales has been made following an 'in-depth analysis of telemetry and data' after the race, adding:

'Yamaha's conclusion is that the rider's actions could have potentially caused significant damage to the engine of his YZR-M1 bike which could have caused serious risks to the rider himself and possibly posed a danger to all other riders in the MotoGP race.'

While the precise nature of Vinales' offending actions wasn't stated, it soon emerged that he had been deliberately and repeatedly over-revving his bike out of frustration with technical problems during the race.

Vinales, who won the season-opening Qatar round before being eclipsed by new team-mate Fabio Quartararo, had already agreed to part ways with the factory at the end of the season, halfway through his contract.

However, the events in Austria meant Vinales wouldn't complete another lap on the M1. An immediate separation from Yamaha was agreed and Vinales went on to finish the season at Aprilia.

Marc Marquez: 'I apologised to Vinales, but it's within the rules'

Not for the first time in 2021, the injured Marc Marquez knew he needed to use every trick in the book to try and advance from Qualifying 1 to Qualifying 2 at Mugello.

In other words, he needed a tow.

This time, the Repsol Honda rider selected Maverick Vinales, quickest of those not to advance directly to Qualifying 2. But the unflinching determination with which Marquez carried out his plan left Vinales visibly frustrated and some felt it crossed the line into unsporting behaviour.

Marquez was one of a number of riders to follow the Monster Yamaha out of the pits for the final Q1 run, but the only one to then also stick with Vinales when he abandoned his out-lap – due to the riders stacked-up behind him - and took a short-cut back to the pits.

With Vinales gesturing and glaring at him as they rode down pit lane, Marquez eventually moved ahead. But it was only a temporary measure. With just minutes remaining Marquez knew Vinales couldn’t pull in again and the #93 was back in his wheeltracks when their flying lap began.

The tactic worked perfectly for Marquez, who was pulled to the top of the timesheets ahead of Vinales with only one lap to go. The Marquez tow soon became even more costly for Vinales when he was pushed down to third, a position confirmed by a mistake on his last lap, leaving him out of Qualifying 2 and 13th on the grid.

Eight-time world champion Marquez, struggling badly for strength in his healing right arm and shoulder, emphasised that what he had done was within the rules, but nonetheless apologised to Vinales.

"We checked the list, the fastest guy was Vinales, so we chose him because he was the fastest guy [not to get into Qualifying 2 directly], but if it was another one [faster] we would choose another one.

"And then just I followed him, it was the tactic because it was the only way to improve.

"I would like to be in another level and another position to push in front and have the others follow me, like many times in the past. But I'm not like this.

"But I know, because I had that feeling in the past, how Maverick can feel. For that reason, I met Maverick before I entered the press conference, where all the TVs are, and first of all I apologised because I know that it's not completely fair, and what I said was 'you have a reason to be angry'.

"But in the end, it's inside the rules. In the limit but inside the rules, and what I did was try to find the perfect situation to do my 100% and to take the best result possible."

Vinales was reluctant to comment on the towing incident, although Yamaha team boss Massimo Meregalli said he hoped Race Direction would look into it.

Asked if Marquez had gone too far in pursuit of a tow or if Vinales had overreacted, reigning world champion Joan Mir said:

"It's always a funny situation, but when you are the one being followed it's not a nice feeling. What I see from the outside is that Marc loves to play and Maverick hates to play. In this situation you cannot do anything but your own work. So it's difficult but it's like this. It's not a Superpole!"

"When a guy wants to follow you that bad there’s not much you can do, except try and do your own lap. I know it’s difficult, but you just try not to get flustered, not let it get into your head or anything like that," agreed Jack Miller.

"But it’s very, very difficult. It's like when you’re a little kid and you’re copying your mum and dad [as a joke] and they say, ‘Stop copying me!’ Vinales slowed down, he slowed down. Vinales sped up, he sped up. They were both in pit lane… It was quite funny to watch. And Enea [Bastianini] was the quiet partner. He was on the back of it. I was hoping he could knock both of them out, ya know?"

Valentino Rossi announces retirement from MotoGP

Having made clear his MotoGP future would depend on results, it wasn't a huge surprise when Valentino Rossi officially announced he would retire at the end of the 2021 season, during a special press conference on Thursday at the Styrian MotoGP in Austria.

But it was still an historic moment, the Italian marking the finishing point for a legendary career that spread across 26 seasons of grand prix racing and nine world championships.

"I've decided to stop at the end of this season so unfortunately this will be my last half-season as a MotoGP rider," Rossi said.

"It’s difficult. It's a sad moment, because it's difficult to say and to know that next year I will not race with a motorcycle. I've done this for more-or-less 30 years! So next year my life will change.

"But anyway it was great. I enjoyed it very much. It was a long, long journey. Really funny. 26 years in the world championship. I've had unforgettable moments with all my team and all my guys that worked for me.

"In all sports, results make the difference, so at the end it's the right way. I had the chance to race for my team in MotoGP together with my brother next year, something that for sure I like.

"But anyway it's okay like this I think… I can't complain about my career!"