Red Bull team boss Christian Horner has said Formula 3 driver Dan Ticktum is nowhere near the level Formula 1 demands, but reckons the 19-year-old can get there with a little more time.
Ticktum was understood to be in the running for the second Toro Rosso seat for the 2019 season, but that hinges on him winning the F3 championship as well as Red Bull being able to convince the FIA to push through a tweaked Superlicence points system which would award points for winning the Macau Grand Prix.
The former now looks unlikely after Mick Schumacher, son of seven-time F1 champion Michael Schumacher, took the lead of the championship, relegating long-time leader Ticktum to second with just one race weekend remaining.
Schumacher's run of five wins in six races has moved the young German 49 points clear of Ticktum, who reacted by hitting out at the situation on his social media.
"Interesting is how I would describe their pace and I am confident many people in the F3 paddock will agree," wrote the Red Bull-backed racer.
"Unfortunately, however, I am fighting a losing battle as my last name is not Schumacher," he added.
Related: Daniel Ticktum lashes out over 'interesting' Schumacher/Prema pace
Horner, speaking to Sky Sports in Russia, said Ticktum needed more time to develop both on and off track before he's ready to step up to F1.
"He's a character. He sometimes engages mouth before brain," Horner said of Ticktum's social media rant.
"[He's] a talented driver, but he’s got more development to do before he’s anywhere near Formula 1 level. He’s fast, but he just needs to polish off a few rough edges.
"In Formula 3 Mick Schumacher is doing a great job, he's obviously been particularly dominant, they've obviously got it together in the second half of the season and he's been the man to beat. He looks very much the favourite to win that championship with one race to go."
Toro Rosso is poised to announce Daniil Kvyat as one of its 2019 drivers this weekend.