Toro Rosso tech boss James Key is highly regarded in the F1 paddock, and Carlos Sainz is pleased to see the engineer remain on-board at Faenza.
Key's contract with Toro Rosso was extended earlier this week, keeping the Briton with the junior Red Bull outfit for a sixth full season.
"I have always said that James is very important for Toro Rosso," said the Spaniard, whose is also set to remain with the team for 2018.
"I don't know for how long he has extended the contract, but I am sure that if every F1 team had the same budget, Toro Rosso would be much higher and in many respects that is due to James," Sainz added.
Toro Rosso held talks with Honda recently, discussing a potential engine partnership with the Japanese manufacturer. But talks were inconclusive, meaning its power will still be supplied by Renault next season.
"To be honest I have nothing to do with that and I have been told nothing by Helmut Marko or anyone else, so I think it's nothing more than rumours," said Sainz.
While most are predicting an extension of Dany Kvyat's contract with Toro Rosso, others insist that 2016 GP2 champion Pierre Gasly is still in the running for a seat next year, a prospect which Sainz would welcome.
"Of course I have sympathy for him and I wouldn't mind if he became my teammate," said Sainz.
"But this is also Helmut Marko's responsibility, not mine, so I have no idea if he will go for stability or get a new talented driver.
"Unfortunately for F1 it's not enough to show excellent results -- a number of circumstances have to come together as well so you need to have patience," he added.
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