Caterham boss Manfredi Ravetto has admitted that he was "surprised" to hear driver Kamui Kobayashi claim that his retirement in last weekend's Russian Grand Prix was down to the team wanting to save mileage.

The 28-year-old told reporters that "the team just decided to stop" when he was called to pull out of the race on Sunday during lap 21.

The team have stated that the reason for Kobayashi's departure was because of overheating brakes.

"Actually, I was very surprised to hear Kamui referring to some mileage-saving instruction coming from the team's management," Autosport.com quotes Ravetto as saying. "We saw via telemetry that there was a potential issue with the brakes and we decided to avoid any risks.

"Kamui officially confirmed this as well and I'd like to add that he had also asked us to change the previous set before qualifying because he felt some vibration. To be clear - yes, we instructed Kamui to retire because the safety of our drivers is our first concern."

Caterham have insisted that there were no problems of component shortage in Sochi.