Toro Rosso's F1 Japanese GP was impossible - Carlos Sainz Jr

Team-mate Daniil Kyvat was the best-placed Toro Rosso in 13th, 24 seconds off the points positions, with Sainz 17th.

The Faenza team has scored just two points in the last six races because its form has as its 2015-specification Ferrari engine has become increasingly uncompetitive.

"The problem with the top speed is it leaves you very little in terms of strategy because we know it is impossible to overtake," said Sainz.

"Today, I wasn't even able to clear a McLaren that is the second slowest car in the field.

"This means that our flexibility on strategy is reduced and the choice they did with me, leaving me out and having to pass five cars at the end was, impossible.

"I tried my best to make the strategy to work but it was impossible with the top speed to do anything."

Based on the speed trap figures from qualifying, which give the most accurate comparison as all cars use the DRS with comparable tyre condition, fuel loads and engine settings, Toro Rosso was the second slowest car on top speed - 6.5mph slower than Mercedes and just 0.4mph faster than McLaren.

Sainz admitted the situation was frustrating but insisted Toro Rosso will work hard to improve the situation.

"This is what we have at the moment and we need to adapt and we need to correct it," he said.

"This weekend, we chose to run our standard downforce without any compromise for our top speed.

"It showed that our qualifying pace improved compared to Malaysia and our race pace probably was worse so we will need to analyse."

Kvyat added: "We have to accept that our straightline speed is too slow to fight for positions.

"There was absolutely nothing left on the table and it's just unfortunate that everyone finished and there was no safety car.

"I had to do miracles to stay ahead, but it meant not keeping my tyres in good shape."