After spending 24 days in isolation, costing him two MotoGP events and Friday practice for a third, Valentino Rossi's Covid-19 nightmare came back to haunt him earlier this week.

Despite last week's negative results, the Italian then gave a 'marginally positive' reading during Tuesday's test at home in Tavullia, prior to attending this weekend's second Valencia round.

Fortunately for Rossi, he still had time to take another pair of tests, 24 hours apart. Both came back as negative, clearing the way for the Yamaha rider to take part in his first full weekend since Le Mans.

"In reality I was not another time positive, but in the Tuesday test there was something not clear," Rossi said. "The doctors said it happens a lot of times, especially to people that had the Covid before, like me.

"But I was very, very worried because, f**k, it's one-month... yes-no, yes-no. It's a long nightmare. So I'm tired. It's normal. But the doctors said 'don't worry, it sometimes happens, we will do Wednesday and Thursday and I promise you will be negative'.

"And in fact it's like this. So I'm happy, I'm here and this is good because now I can do a normal weekend working from Thursday and riding from Friday."

With his own medical scare over, Rossi was asked for his thoughts on the news that six time MotoGP champion Marc Marquez will not compete again this season, due to a slow recovery after twice needing surgery on a broken right arm.

"It was a bad injury already the first time, after the crash, because that bone is very important to ride the bike. But the bigger problem is the second [operation]." Rossi said.

"He tried everything to come back in just some days, but at the end this created a big, big problem so now it will need a lot more time."

The worst season of Rossi's career in terms of injuries was 2010, when he suffered a shoulder injury while training on a motocross bike, then broke his leg at Mugello. The leg was pinned immediately, while the shoulder was repaired with surgery at the end of the season.

"In the end we are humans and with your body you always have to have a big respect. After a hard injury you need to look at the long future more than the close future because it's not just your career, but your life," he said of his experiences.

"For me [in 2010] it was difficult because I had a bad injury to the shoulder, but I wanted to come back and keep riding and at the end I had the injury also to my leg. So it was a very difficult season, because I feel very very bad.

"In the end everything can happen in this sport, but you need to remain strong and try to fix step-by-step, but sometimes you need time."

Another topic in a big week of MotoGP news is that Cal Crutchlow is set to take over from Jorge Lorenzo as the official test rider for Yamaha next season.

"Sincerely I don't know if he's already signed or not, but for me Cal is a good idea because he's fast and he's still a rider," Rossi said. "So I'm happy because Cal and I have a good relationship, but I also think that Dovizioso can be a very good option for Yamaha."

Better than Lorenzo?

"When I knew about Jorge [joining Yamaha as test rider this season] I was very happy, because Jorge is great to ride the M1. But depends, I think that Dovi and Crutchlow race also this year, so maybe they are more ready."

Dovizioso has said that, after talks with several manufacturers, he has decided against signing any test deals for 2021.