Sainz says Renault engine issues were to be expected

The Toro Rosso driver admits, however, that the lack of running during the first Barcelona test has been far from ideal.

The Faenza-based squad, which is using Renault engines again this year after switching from Ferrari units, has lost valuable track time over the course of the test, and Sainz was forced to stop early on Wednesday after a problem with his power unit.

The team also lost the morning of the final day of work after it was force to replace the engine in Daniil Kvyat's car.

With Renault having opted for a new design for its engine, Sainz says he expected the first test to be difficult, but he insists he will not complain if Renault delivers the promised step forward once the season starts.

"We knew it was going to be a tough first test," said Sainz. "Especially because the engine is completely new. It's a bit like nearly a start from zero from there, so it was obviously not gonna be easy.

"But of course we would have liked to do some more laps these last couple of days, but we need to give them time. The whole team will tell you that we would have liked to do more laps and to complete a bigger part of the programme.

"They have done a fully new engine that they are predicting a good step on power, so as long as this power is delivered in the first race, I'm not going to complain at all."

Sainz acknowledges that the second test next week needs to be better for both Renault and his team.

"I think now the main focus is to improve the reliability," he said. "I think they are the first ones to know that the big margin of improvement now is in that point.

"I'm not going to apply any kind of pressure or anything, because they already know that we need to keep working on that and start adding some laps to our lap count."

While Sainz says he has been happy with the STR12 car, the Spaniard concedes that he has no idea where the team stands in the pecking order as he has not been able to push.

"We stopped when we were starting to have a bit of pace in the test and it's a shame because now is the time to do miles and we couldn't do as many as I would have liked," he said.

"It was the first day that we had to push a bit and we weren't able to.

"Until I can do long stints, with at least 10-15 laps to see how the tyre degrades, I won't be able to push to the limit."