Alonso Mercedes' back-up plan should Hamilton leave

Mercedes have reportedly put a 'Plan B' in place should contract negotiations with Lewis Hamilton fail to materialise for the 2016 season.

The Briton is already contracted for next year alongside title rival Nico Rosberg, but should Hamilton fail to sign a contract extension for 2016 and beyond, then Fernando Alonso could likely take his seat.

According to paddock sources, that might explain why Alonso and McLaren have yet to agree a deal as the Spaniard is looking for a single-season contract with options to continue if Hamilton remains with the Silver Arrows.

McLaren however are looking to sign the Ferrari driver for at least two years, but know they can't offer performance guarantees and are therefore in a difficult position to negotiate.

If a one-year deal isn't on the table, then Alonso may be forced to take a sabbatical to ensure he is in a prime position when it comes to agreeing drivers for 2016 - but that decision could backfire if the top teams (Ferrari, Red Bull, Mercedes, McLaren and Williams) have all agreed long-term deals by then.

It leaves the two-time champion in a difficult position as he chases the best possible seat to ensure him of a so desperately wanted third title.