Pierre Gasly's ongoing struggles to get on the pace of teammate Max Verstappen has prompted rumours about the Frenchman's future, following his promotion from Toro Rosso at the end of last season.

While Red Bull's motorsport advisor Helmut Marko has repeatedly dismissed talk that the team is considering a mid-season change, it is obvious that Gasly will need to improve if he is to guarantee his seat for 2020.

With Toro Rosso's Alex Albon still in his rookie season, it is unlikely he would get the nod for next year as a potential replacement; especially if the parent team concludes that Gasly was promoted too quickly.

That would therefore leave Kvyat as the most likely option to move up, the Russian having already gained experience previously at Red Bull during his tenure there in 2015 and the start of 2016.

But although a return for Kvyat to the team that sacked him would be remarkable, Tost does not see a problem with it – and certainly thinks it would not be embarrassing.

"No, I don't see it as a loss of face," Tost said in an interview with the 'Starting Grid' podcast. "The decisive factor in Formula 1 is performance. If a driver delivers the performance, why not bring him back? If you are convinced that it is the right choice."

Tost is far from dismissive about the potential for Kvyat to move to Red Bull again, and he reckons the Russian would shine.

"Dany Kvyat is a Red Bull driver," added Tost. "He is currently on loan to Toro Rosso. We'll see how all this pans out in the future. I would be happy if Dany could return to a top team, thus Red Bull. Why? Because I think he has the speed. If all the circumstances there are right, he can perform very well."

Tost, who worked with Gasly last year, says he did not expect the youngster to have such a tough time in making the move up to Red Bull.

"I'm a bit surprised myself because I think Pierre Gasly is a lot better and faster than he seems to be at the moment," he said. "But I don't know the exact circumstances."

Asked about the bad press that Gasly was getting, Tost said: "That's Formula 1! This is a high performance area. If you don't deliver the expected performance, you will be criticised. You have to be able to deal with that."

Lack of confidence

Pierre Gasly, Red Bull Racing RB15, leaves the garage Photo by: Steven Tee / LAT Images

Earlier this year, Tost reckoned that Gasly's speed was being hurt by a lack of confidence with the rear end of the Red Bull.

Speaking to Motorsport.com, Tost said: "He can't cope with the car like that. The car is unpredictable for him, light on the rear axle, and that's something he doesn't like. He likes a stable rear axle. It's not because he lacks talent, but because he lacks experience."

"And two factors come together. First, Verstappen with his own level of natural speed. Second, that the car concept doesn't suit Gasly one hundred percent. These two factors are enough to lose two or three hundredths of a second in every corner. If that's 15 corners, that's three or four tenths of a second."