Red Bull chief Christian Horner doubts Sebastien Buemi will make a shock return to a Formula 1 race seat in 2019 due to his existing commitments in other championships.

Buemi raced in F1 with Toro Rosso between 2009 and 2011 before being dropped by the team, albeit remaining part of the Red Bull family as its official reserve driver.

Since losing his F1 seat, Buemi has gone on to win titles in both the FIA World Endurance Championship and Formula E, and took his maiden 24 Hours of Le Mans victory in June with Toyota. He is also racing for Nissan in Formula E’s fifth season, starting this December.

Speculation emerged in recent weeks that Buemi could be in line for a possible F1 return in 2019 with Toro Rosso as the team considers options including twice-dropped Daniil Kvyat for next year.

Buemi has been present in the F1 paddock in Singapore this weekend, but senior Red Bull team boss Horner cast doubt on the possibility of a return for the Swiss racer.

“Sebastien’s done a great job. He’s won Le Mans this year, he partnered with Fernando [Alonso] obviously, he’s Formula E he’s been champion there,” Horner told Sky Sports F1.

“He’s an important part of our team going forward, and there’s a few other teams that are interested with the role that he’s been doing.

“But he’s committed for the next three years with the team in the role that he’s doing. He’ll be combining that with his other activities.

“I don’t think Formula 1 racing is on his agenda. He’s got his Formula E program, he’s got his Le Mans program, he does a wonderful job for us in the sim. I think that’s more than enough for him.

“People would have to take a big pay cut to come back into Formula 1.”

Toro Rosso is one of four teams yet to confirm either of its drivers for 2019. Of its current line-up, Pierre Gasly will move up to Red Bull for next year, while teammate Brendon Hartley’s position is known to be at risk.

Crash.net understands that Kvyat is increasingly likely to make a shock return to Toro Rosso next year, but the second seat has a number of potential candidates.

Mercedes youngsters Esteban Ocon and George Russell are both searching for F1 seats, but Red Bull is known to be unwilling to take on a driver linked to the German manufacturer at its junior team.

Mercedes announced on Friday it would be parting company with recent F1 driver Pascal Wehrlein at the end of the year after failing to secure him a competitive drive for 2019, but the German is understood to be more likely to end up in Formula E for next season.

Other drivers looking for F1 seats in 2019 include Stoffel Vandoorne, who will leave McLaren at the end of the season, and Ferrari youngster Antonio Giovinazzi, who is in contention to partner Kimi Raikkonen at Sauber.