Another candidate to become Sebastian Vettel's new teammate at Red Bull has emerged in the form of Mercedes driver Nico Rosberg.
Germany's Bild newspaper said the 25-year-old, who has been so impressive alongside famous teammate Michael Schumacher in 2010 and 2011, could theoretically escape from his current contract at the end of the season.
Mark Webber's Red Bull deal also ends this year, and there has been much speculation about Lewis Hamilton possibly leaving McLaren to join the reigning champions.
Red Bull driver manager Helmut Marko told the newspaper: "Nico is a strong driver."
German Rosberg, however, said only that Mercedes is "focused on our fightback".
And Mercedes competition director Norbert Haug has warned that the Silver Arrow should not be written off.
"Our car certainly has its strengths and weaknesses. We will remove the weaknesses gradually and be competitive," he added.