In last weekend's Chinese Grand Prix the reigning world champion was told for the second successive race to move aside for his quicker team-mate, and he was reluctant to do so.
Although Ricciardo has impressed his team since stepping in to the seat vacated by Mark Webber, Red Bull boss Christian Horner has revealed that Vettel is having problems with the RB10.
"I think that Sebastian is having a tough time at the moment because he hasn't got that feeling from the car that he is looking for," said Horner.
"He is tremendously sensitive to certain aspects of the set-up, and he is not getting the feedback from the car he wants.
"The compound effect of that is that he is damaging the tyre more, which is very unusual for Seb.
"We have seen since Pirellis have been introduced [in 2011], that it is highly unusual for him to be going through the tyre life quicker than the average.
"I think that is just a culmination of the issues that he has currently. But as soon as he has worked them out, he will be back with a bang."
Horner added that while Vettel is struggling at the moment, Ricciardo's weekend in China was great.
"It is a massive performance from Daniel," said Horner. "He has been hugely impressive all weekend.
"He has really been outstanding this season in all four grands prix this year. He has done a tremendous job.
"His confidence is growing, he seems so calm in the car, his feedback is exceptional, and when he talks on the radio it is like he is in a coffee shop up the road.
"He is enjoying what he is doing. He is enjoying being a grand prix driver, and he is enjoying driving for the team."
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