Nine-time world champion Valentino Rossi will concentrate on sorting out braking issues that have reared their ugly head again for the Italian at Laguna Seca.

After changing fork settings at the Aragon test and then refining the setup over the past two races, it was thought Rossi had eliminated the problem but the heavy, downhill braking areas at the California track are causing him problems - as is the pace of Marc Marquez.

"The first day of practice is not so bad. This afternoon I am in fourth position but not very far. We have to concentrate yes on the speed but especially on pace, try to have a good setting for the bike which doesn't slide too much on the rear," said Rossi, speaking at Laguna.

"I am not too fantastic on braking, especially going downhill so it means we have to work on the balance and the electronics of the bike. It is true that Marquez have something more, so I have to make another step.

"This afternoon I tried to do 30 lap with the same tyre and too have the good feeling to understand what happens because I think that we have to concentrate very much on the second half of the race when the tyres start to slide and lose some grip.

"From one side, I am not surprised that Marquez is so fast, he is a fucking bastard like I said last week but maybe he is more a bastard than what I think before. This is a track that is good for him, his style and his Honda but it is impressive."