Valentino Rossi is confident that fifth place in Friday practice does not represent his true potential in this weekend's Americas MotoGP at Austin, Texas.

The nine-time world champion is anxious for a strong showing this weekend to prove his progress after struggling to sixth in the inaugural 2013 COTA event.

The Italian was at least the quickest Yamaha on Friday, albeit 1.3s behind Honda's Marc Marquez. Like Marquez, Rossi spent a lot of time working on the harder tyre, which Marquez took to victory by 0.2s over Rossi in round one at Qatar.

By contrast, two of the Ducati riders ahead of Rossi used the Open class soft tyre to set their best lap time.

"I'm quite satisfied about today because I already have a good feeling with the bike. We have a lot to improve but the general balance of the bike is not so bad," said Rossi.

"This morning I was fourth and this afternoon I am fifth. I'm not happy with that because I have a better potential, but I don't work well with the soft tyre yet. This afternoon we focussed on the harder tyre and I'll be happy if I can make that work for the race.

"I had the possibility to go a bit faster and stay with the top three but I'm not yet able to use the maximum potential of the tyre. We have to work to improve the balance and the setting. I think I can stay with Lorenzo and Pedrosa, but Marquez I'm not sure."

Team director Massimo Meregalli insists they can prevent a repeat of last year's Repsol Honda one-two.

"There is a gap to the front at the moment but we are honestly in a better position than last year when we started here so I am confident we can improve session by session, exactly as we did at the last round in Qatar," said team director Massimo Meregalli.

"I believe Vale's gap to the front would have been smaller if he had been using a softer tyre but he spent most of the second session working with the hardest option to see what was possible."

Rossi had been fifth and 1.8s behind Marquez after day one of last year's event.

Team-mate Jorge Lorenzo was eighth fastest on Friday.