Carlos Sainz says he still expects Toro Rosso to be chasing Red Bull when the 2016 Formula 1 season gets underway, despite the assertion from its team boss Christian Horner that the switch to Ferrari engines is worth up to 0.8secs per lap.

After months of wrangling as relations between Red Bull and engine supplier Renault broke down, sister team Toro Rosso accepted an offer from Ferrari to use year-old power units in 2016, whereas Red Bull will stick with the French firm, albeit under the TAG-Heuer moniker.

With Horner still expressing misgivings about having to remain with Renault - having been turned down by Ferrari and Mercedes -, he feels Toro Rosso, even with its dated engine, stands to gain 0.8secs per lap, which he believes would place the 'B' outfit ahead.

However, though Sainz acknowledges that Toro Rosso have indeed had a strong build up to the season, particularly in terms of reliability, he doesn't expect to have a Red Bull behind him come the Australian Grand Prix.

"We will see," he told Crash.net. "It wouldn't be bad. Eight tenths I will put in the pocket and we go to Australia! We still don't know how much it is worth on track. We have simulations, we have all these tools but we will really need to see it in Australia."

"I cannot disagree with my boss but I can be a bit calm and moderate than him. Red Bull last year were six-tenths in front of us and the Ferrari engine should give us those six-tenths but Red Bull in the winter should do a massive step compared to Toro Rosso due to budget so they should still be in front in my opinion.

"They have a much bigger budget and a Renault power unit which will be developed over the year. I expect them to be in front."