Ferrari was known to be keen on placing both its outstanding junior drivers, Charles Leclerc and Antonio Giovinazzi, at Sauber for 2018 as part of an expanded technical partnership with the team.
The line-up was announced at a special press event in Milan, Italy on Saturday, where the team revealed further details of their new title sponsorship deal with Alfa Romeo, including a revised red and white livery concept for next season's auto and a new logo. The Italian vehicle manufacturer is making a return to the sport after 30-years to sponsor the team.
Sauber, meanwhile, had Marcus Ericsson angling for a seat despite not scoring any points in either of the last two seasons, relying heavily on his links to the team's owners.
"It was a great experience to drive a few FP1 sessions and tyre tests for the Sauber F1 Team in 2017, during which the team welcomed me straight away", said Leclerc. Instead, the Italian will be Sauber's third driver, effectively meaning he is in a reserve role. Having used a year-old power unit this season, next year will see Sauber running the latest specification in a deal that has since been extended to the Alfa Romeo partnership.
"Now there is the additional benefit that when we sit down at the table to discuss the future of Formula One, we're playing two marques", he told reporters.
It's been a busy year for Sauber. "First and foremost, I would like to thank Ferrari for their support".
"I think obviously we're starting from quite far behind because we had a hard season, but I think we have the potential to take a good step forward".
"I am very happy to be entering Formula 1 in 2018", said Leclerc.
Alfa Romeo supplied engines in the 1960s and 1970s and returned as a constructor in 1979 before again withdrawing at the end of 1985.