Toro Rosso's Franz Tost believes Red Bull's Junior Team remains a good project, adding that Max Verstappen and Carlos Sainz Jr are "two diamonds".
The Faenza-based squad have been part of the programme for years and Tost have nurtured several drivers who have gone on to drive for the main Red Bull Racing outfit.
"If you look at the results, I would say yes (it is still feasible)," the STR team prinicipal told the official Formula 1 website. "The original plan from Red Bull was – and remains – that Toro Rosso give young drivers from the Red Bull driver pool the possibility to enter F1.
"So far it’s worked very successfully if you think that Sebastian Vettel came from Toro Rosso, as did Daniel Ricciardo and Daniil Kvyat. I think with Max and Carlos we have two other diamonds in Red Bull hands. I think if you bring all the factors together, it’s still feasible to go this way."
STR will have the youngest-ever F1 line-up this year with 17-year-old Verstappen set to become the youngest ever race when he competes at the Australian GP while Sainz Jr is only three years older.
The pair have been solid during pre-season so far and Tost feels it will be difficult to separate them during the season.
"I have quite positive impressions from both of them," he said. "Both are much more mature than people maybe would expect. Both have shown very good performance – they are very committed and very motivated.
"I expect that they will be closely matched – one might sometimes have an advantage in qualifying and the other will maybe be faster in the race, but in the end I think both of them, on the performance side, will be quite equal."