Former Formula 1 world champion Jacques Villeneuve believes Daniil Kvyat did not produce strong enough results in 2016 to be kept on by "retirement team" Scuderia Toro Rosso.
The Russian, who was demoted from the main Red Bull Racing squad to sister team Toro Rosso four races into the 2016 season, was announced as an STR driver for next year during the United States GP weekend.
Commenting on Red Bull's decision to retain Kvyat, the famously outspoken Villeneuve suggested the call was not made on the basis of results alone.
"It's surprising, because his results did not advocate for him to stay in F1. But they must see something in the way he works that is promising, I guess."
Since his demotion to Toro Rosso in May, Kvyat scored four championship points in 14 grands prix, while teammate Carlos Sainz collected 34.
And while many, including team boss Franz Tost, have said that Kvyat had made tangible progress after his STR return, Villeneuve did not agree with those claims.
"He [Kvyat] hasn't made any improvements since he's been down at Toro Rosso," Villeneuve said.
"He's been getting it from Sainz. He's not at that level.
"And Toro Rosso is not a team to keep drivers. So there must be a reason, that they think is good for the team. Maybe he is working super well and he's helping developing the car. That from the outside we cannot know."
Asked whether Sainz or Kvyat were likely to challenge Red Bull's main duo Daniel Ricciardo and Max Verstappen for seats in the energy drink giant's lead F1 team, Villeneuve said: "No. Red Bull are happy with their two drivers. They have their two star drivers.
He also said: "It [Toro Rosso] is becoming a retirement team."
Interview by Erwin Jaeggi