Fernando Alonso would be top of the list for Mercedes if Formula One champion Lewis Hamilton fails to agree a new deal with the team beyond this year, according to motorsport director Toto Wolff.
Hamilton, who took his second championship in 2014 after winning 11 races, has yet to put pen to paper on a new contract despite both sides talking about their eagerness to stay together.
Wolff says the priority is to continue with Hamilton and Nico Rosberg, but if a deal can't be completed then Alonso would be their next target.
McLaren said last month that Spaniard Alonso, a double world champion, had signed a multi-year deal in joining them from Ferrari.
However, Alonso made little secret of the fact that he was interested in the Mercedes seat and is likely to have exit clauses if McLaren, who are starting a new partnership with Honda after years with Mercedes, under-perform.