Toro Rosso are yet to "100 per cent" understand why Daniil Kvyat experienced two punctures during practice for the Abu Dhabi Grand Prix.
The Russian finished slowest in both sessions as the punctures, one in each practice session, forced him to stay in the garage, whilst team-mate Carlos Sainz was also called in as a precautionary measure.
It's not yet been determined how the punctures were caused, but it's suspected that either debris or a bodywork issue are to blame, rather than the tyre itself.
"After facing two failures on the rear rim of Daniil’s car, it was decided to avoid sending Carlos out on track again because we still haven’t understood 100 per cent where the problem is coming from," team principal Franz Tost said.
"We will now work hard tonight, together with the engineers back in Faenza, and hopefully we will sort it out for tomorrow."
