Mark Webber's tenure at Red Bull Racing has been the subject of scrutiny for several years, but the Milton Keynes team may finally have settled on a replacement for the Australian should he not live up to expectation in 2013.

While both sides have been happy to ink single-year extensions to his contract over recent seasons, the belief is that Webber is now facing the exit from F1's top team, particularly if he does not toe the line when it comes to supporting team-mate Sebastian Vettel. The German has been top dog at RBR for the past three seasons - at least as far as the points tables are concerned - but Webber has done his best to try and prove team boss Christian Horner's tenet that there is no favouritism by refusing to make life easy for the German.

Matters appeared to take a twist when the Australian did not yield to Vettel's recovery drive in the decisive Brazilian Grand Prix - prompting one insider to claim that two drivers, Webber and Felipe Massa, were working in Fernando Alonso's corner at Interlagos - and Red Bull motorsport advisor Helmut Marko has suggested that that could have been the final straw for the 36-year old.

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Having already suggested that he does not expect the 'balance of power' to change at RBR in 2013 [ see separate story], Marko hinted that he had already lined up a replacement for Webber.

According to Germany's Sport Bild, that may not be either of the current Red Bull development drivers looking to step up to the 'first team' from Toro Rosso, with the Austrian apparently keen to snatch Nico Hulkenberg from under the nose of rival Ferrari.

The German swaps Force India for Sauber in 2013 in a move that many believe primes him to become the natural successor to Massa when the new F1 regulations come into force in 2014, but Marko was also clearly impressed by his showing last season.

"A few years ago, he was on the list of candidates for our junior team," the Austrian explained, "However, Nico already had a main sponsor [Dekra] with which he didn't want to separate."

Hulkenberg's one-year deal with Sauber paves the way for him to move on at the end of the season and, given the chances of Vettel remaining at RBR for the foreseeable future - despite rumours of a move to Ferrari - could be bad news for both Daniel Ricciardo and Jean-Eric Vergne, despite the pair having been given another year to impress at Toro Rosso in 2013.

Hulkenberg headed into the winter break having created a positive impression on many in the F1 paddock by leading comfortably at the Brazilian Grand Prix. Only an error while trying to retake the lead from Lewis Hamilton - which led to the Briton's retirement - blotted his copybook, but the German went on to finish fifth on the road, and featured prominently in end-of-season reviews.