Rossi had made a spectacular start to his return to Yamaha when he surged through the field to take second in the Qatar season-opener.
But he struggled at the following race at Austin, where amid a weekend of brake problems he could only qualify eighth and finish sixth.
Although Honda dominated the event, Rossi's team-mate Jorge Lorenzo was still able to finish on the podium.
Rossi is adamant that his Texas slump will prove to be a one-off and that this weekend's Jerez race will be better. The Spanish track was the scene of a major step for Rossi in winter testing.
"Jerez will be a very important race. I believe and hope that we can be very fast, as we have been in testing," he said.
"We still have something to do, especially for the set up of the bike but we have some ideas.
"Furthermore on Monday after the race we will be testing there and we'll have the opportunity to try different things.
"Jerez, Le Mans and Mugello are all circuits that are favourable to us and where we will be fine."
Yamaha goes into Jerez tied with Honda for the lead of the manufacturers' championship, while Lorenzo and Marc Marquez share the lead of the riders' points.
Rossi is fourth, 11 points adrift.
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