With double world champion Lewis Hamilton out of contract at the end of the season and talks yet to restart over a new deal, Mercedes’ Toto Wolff has already highlighted Alonso and Valtteri Bottas as his main targets if Hamilton needed to be replaced.
With Alonso believed to have approached Mercedes during 2014 when negotiating his release from Ferrari, Wolff’s comments hinted that it could be possible for Alonso to leave McLaren at the end of this season despite having joined on a multi-year contract.
For example, such a scenario would have been possible if Alonso had a clause allowing him to move to the world championship-winning team, or a team which finished in the top two of the constructors’ championship if McLaren was lower than a specified position, but Dennis says no such clauses are in place.
"No McLaren driver has ever had performance clauses in his contract and that's the case with Fernando,” he told BBC Sport.
Alonso himself said at the launch of the new McLaren MP4-30 that he is expecting a tough start to the season with new power unit supplier Honda.