Marc Marquez says his 2017 MotoGP championship battle with Andrea Dovizioso has taught him not to underestimate any of the riders in the category in future.
Ducati rider Dovizioso emerged as Marquez's main rival this year, taking the championship battle to the final race at Valencia before losing out to the now-four time champion.
But Marquez accepts that he did not view the Italian as one of his likely challengers for 2017, and he says he will not make that mistake again.
"This year, when people were asking me which rival, which opponent is the most dangerous, I was always saying Maverick [Vinales], Dani [Pedrosa], Valentino [Rossi], maybe [Jorge] Lorenzo, but I never said Dovi," said Marquez.
"It's something I learned this year, that you need to be careful with everybody and try to pay attention to everybody.
"In the beginning of the season it looked like Maverick was the fastest one, but in the end the most constant, the most complete guy to fight for the title was Dovi, and it was so nice to fight with him."
Marquez added that he and Dovizioso have a good relationship, and that neither rider overstepped the mark when they were battling each other on track.
"He is a kind of friend in the paddock," he said. "But when you are on the track, you don't have friends.
"Always we try to have that respect but we are riding on the limit, fairing with fairing, elbow with elbow, trying to do 100%.
"Some nice battles, and he won every battle. If you check, Austria and Japan, he beat me, but they were circuits where I was struggling and I arrived in the end with him.
"He deserves also to be in my place [as champion], because he did an incredible season."