Sebastian Vettel has indicated that unspecified damage to his chassis may have contributed to his lack of pace relative to his teammate, the dominant Webber, in Spain and Monaco.
It was those back-to-back races that Mark Webber won commandingly from pole, and after which Red Bull decided to replace the sister RB6 driven by 22-year-old Vettel.
"I think it (the damage) explains a lot and on top of that we found also other things that weren't in proper shape anymore," he told reporters in Turkey.
Asked to specify how the damage affected his recent pace, Vettel added: "It's difficult to say.
"Whereas he (Webber) always seemed to be quite happy, I wasn't."
Webber was also asked at Istanbul Park about Vettel's chassis switch, and how the situation might explain the outcome of the Spain/Monaco double header.
"Obviously I wasn't driving his car, so it's difficult to know, to be honest. We'll see," the Australian said.
Vettel names new chassis 'Randy Mandy'
Sebastian Vettel has named his latest RB6 chassis 'Randy Mandy'.
Giving his cars an amorous female name has become one of the 22-year-old German's several F1-related superstitions.
He religiously steps into his cars and dismounts from the left-hand side, and slides a lucky coin behind the laces of his boot.
Vettel called his original 2010 Red Bull 'Luscious Liz', following on from its 2009 predecessor 'Kate's Dirty Sister'.
But Luscious Liz has been retired after the team found damage in the wake of the Spain/Monaco double-header, dominated emphatically by his teammate Mark Webber.
It emerges that Vettel will now be at the wheel of the fully-updated test car.
It has been a warm and sunny day at Istanbul Park, and more of the same 't-shirt weather' is expected throughout the Turkish GP weekend.