Toro Rosso team principal Franz Tost insists that there is still more to come from Jean-Eric Vergne, who is contesting his third season with the squad.
Vergne made his debut in 2012 but missed out on a Red Bull seat for 2014 and remained with Toro Rosso, alongside rookie team-mate Daniil Kvyat.
Vergne has scored nine points across the opening 10 races of the year but has frequently been halted by issues with the Frenchman having retired from half of the races.
"He has suffered a lot with reliability issues, but when his car was running fine, he delivered good performances," said Tost.
"Thanks to his experience he makes an important contribution to the team’s technical development and I’m convinced that there is still more to come from him."
Tost also had praise for Kvyat, who has taken six points from the first half of the season.
"He is doing a very good job, taking into consideration how little mileage he was able to do before the season, he is driving very
well, showing that he has natural speed," he said. "He is doing a fantastic job."