Nine-time world champion Valentino Rossi has said his 2013 switch back to Yamaha is a brave choice as he could have sat back and raked in 'a lot of money' had he stayed with Ducati.

The Doctor said he needs to find out if he is still a top rider and the best way to do it is to go up against old nemesis Jorge Lorenzo on the same machinery.

"For me next year will be very crucial because I did a very brave choice. I want to understand if I am still a top rider. I had a quite safe position if I remain in Ducati, I will take a lot a lot of money and I can stay and if the result doesn't arrive but if I ride the M1, together with Lorenzo, I have to make the maximum," said Rossi, speaking to bikesportnews.com at Indianapolis.

"I have to train the maximum, concentrate the maximum, put all the things together at the top level and try to understand if I am still at the top. I think it will be difficult because Lorenzo is very strong and also the other guys but I think anyway I can make some good result."