Sky Sports commentator Martin Brundle believes Fernando Alonso will "probably" fill a vacant seat left by Daniel Ricciardo at Renault.

The news on Tuesday that Sebastian Vettel will leave Ferrari after the 2020 season has caused a ripple effect across the grid, with Carlos Sainz expected to join from McLaren and Ricciardo tipped to take the Spaniard's seat at McLaren.

That would leave the French manufacturer facing a dilemma as to whether they promote one of the Academy drivers, such as Guanyu Zhou and Christian Lundgaard, or pick a more established driver.

"This is a really strange time in that driver contracts are coming to their end, to fruition, and teams are having to make decisions based on the future, with no current season as an indicator," Brundle told Sky Sports on Tuesday.

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"So this plays into the hands of young but experienced young drivers. The new kids in town haven't had a chance to prove themselves as a Leclerc or a [Max] Verstappen, for example.

"They're working blind at the moment, but I see a scenario that is [Carlos] Sainz to Ferrari, Daniel Ricciardo to McLaren, and then that leaves a seat at Renault which probably would be Alonso."

Only last week, the double world champion appeared to rule out F1 as an option for 2021, hinting a return to the Dakar Rally and WEC holds more appeal.

Still, given his past association with Renault, Alonso is always likely to be a name that first comes to mind when a seat does indeed become free.

If Fernando does say no, however, Brundle thinks Vettel may be an option.

"I think that there's a good chance that Sebastian will step away from Formula 1," the former McLaren driver claimed. "Whether it's for good or not, as we've seen with other drivers, remains to be seen.

"The Renault seat, if I'm right in Ricciardo going to McLaren, the Renault seat is a works seat and may appeal to him."