MotoGP legend Valentino Rossi has admitted he faces a major challenge to beat team-mate Jorge Lorenzo on his return to Yamaha next season.
Rossi previously raced alongside Lorenzo from 2008-2010, winning the title in '08 and '09. But Lorenzo grew ever stronger and was leading the championship when Rossi broke his leg during 2010.
Rossi has been winless since joining Ducati at the end of that year, while Lorenzo has continued to carry the Yamaha challenge.
The Spaniard has taken eight more victories since Rossi's departure and currently leads this year's championship by 23 points, as he seeks to secure a second MotoGP crown.
“It will be interesting,” said Rossi at Indianapolis on Thursday, ahead of this weekend's grand prix. “Now the situation has changed a lot compared to 2008 when Jorge arrived at Yamaha.
“Now he's the No. 1 in the team, and our relationship is good. I have respect for him, and he has respect for me. I am sure that together we can form a great team for Yamaha.”
Rossi added: “The next two seasons for me will be hard, especially trying to stay with Jorge, also to beat Jorge, because now he's very, very fast.
“But I needed a bike for enjoy [racing]. At this moment of my career I have to enjoy, I have to try to fight and to arrive happy at the racetrack.”
An eighth premier-class title would tie Giacomo Agostini's all-time record, but Rossi claims he must first prove that he is still a top rider.