Sainz has comfortably outperformed his former junior single-seater teammate Kvyat ever since the Russian's demotion from Red Bull.

But Tost reckons that balance of power might not last for much longer, as Kvyat regains confidence and the gap between teammates closes up.

"They have a good relationship," Tost said of his two drivers in an interview with Motorsport.com.

"They know each other from the times before. But wait a little bit until they are closer - the game starts once more. That’s normal.

"Because there is no difference whether it’s Max Verstappen, Daniil Kvyat or Carlos Sainz.

"Currently we have quite an easy life because Carlos is ahead. I expect that it will change as soon as they will come closer together and then they will fight each other at the track and then they will touch or whatever. The usual story. This is how it is.

"You can tell them one hundred thousand times ‘you must not do this, you must not do that’, and they are racing and that’s how it is.

"I expect that from this point of view the second half of the season will become more complicated."

Kvyat to bounce back

Backing Kvyat to recover from his mid-season slump, Tost insisted the most important thing for the Russian was to regain self-confidence.

"It takes a little bit of time for him to come back mentally, to calm down, to forget the disappointment, to reset everything, to start once more from a certain level and to improve.

"But this takes time. It’s not from one day to the next day.”

“It is always more difficult to bring the head in the correct way, because the car you can set up, you can change things, dampers, whatever. The head you can’t change so easy.

“It’s self-confidence that he needs. Once this is back, we all know that he is fast, he will fight for points."

Looking back at "stupid" Australia row

The biggest flare-up of intra-team controversy in Toro Rosso in 2016 dates back to the season opener in Australia.

Max Verstappen was left fuming when he dropped behind Sainz due to strategy and a slow stop, with the Spaniard subsequently refusing to make way and eventually being hit by Verstappen.

"[In] Australia, it was a little bit disappointing how stupid it worked," Tost recalled.

"Because Carlos had a problem under the safety car with the front locking and therefore had a lot of vibrations - and we had to call him in because of safety reasons.

"And Max thought we want to undercut him and comes in without telling anything. 'Hey, come on!'

"Max would have finished the race easy on the fifth place, because he was far. But that is part of the learning process. You can’t expect having two youngsters in the team, that everything works smooth. It’s not possible.

"These are exactly the, let me say, mistakes young drivers do and have to do to learn all this. But once more, that’s normal. It is part of the education process."

Interview by Jonathan Noble and Oleg Karpov