AUSTIN, Texas, Oct 26 - Mercedes F1 boss Toto Wolff has backed George Russell for future success after Red Bull's former motorsport adviser Helmut Marko dismissed the Briton's chances of ever recovering from being eclipsed by teammate Kimi Antonelli.

Antonelli is 123 points clear of Russell atop the Formula One standings, with 125 still to be won, and is set to become the sport's youngest-ever champion in Mexico City this weekend as well as the first Italian champion since 1953.

The 20-year-old has now won nine times in his second season to three for the more experienced Russell, who started the year as the bookmakers' favourite.

"Russell is no longer the number one driver." Marko, who left Red Bull last year, told Sky Germany ahead of Sunday's US Grand Prix, which Antonelli won from pole while Russell laboured home in eighth after collecting a five-second penalty.

"Antonelli has quite clearly taken that spot from him ... I doubt whether he'll ever have another chance at the world title or be given number one status anywhere," added the 83-year-old.

Wolff said while he respected the opinion of his fellow Austrian "not-so buddy", Marko was wrong.

"George has all the ability. I think the car doesn't suit him," he told reporters at the Circuit of the Americas.

"At the beginning of the season it's maybe difficult to cope with a situation where you're feeling like this is my year to come and then you have this wunderkind on the other side (of the garage) that starts to really chip away.

"I believe that in a new season, George -- if we provide him with a quick car -- has absolutely what he needs to win a championship.

"I think it's a bit too easy to say let's forget about all these years where he won in F2 and in F3, in his rookie years in the European championships back-to-back in kart. That's all still there." REUTERS