Max Verstappen was upbeat about Toro Rosso's performance and reliability despite suffering a puncture during the final day of the opening test in Spain.
Verstappen completed 110 laps in the STR11 and ended the day in fifth place, but had to return to the pits in the afternoon session when he suffered a left rear puncture in the final sector.
Verstappen did well to retain control of his car at Turn 12, before recovering to the pit lane for fresh rubber.
"I had a puncture but I don’t really know why so we are still investigating that and I’ll find out why," he explained.
"We focused a lot on long running and getting used to the car also for myself, I think it was again a very positive day, enjoyed it a lot
"The car is reacting to what we want and what I want so that is positive. For us it was a very good first four days."