He'll have a new partner for the season, with Formula 2 champion Charles Leclerc stepping up to make his F1 race début in Melbourne.
Fiat Chrysler have invested billions of euros since 2014 to develop new Alfa Romeo models that would stand up against German premium rivals and shed a reputation for poor quality and service that has hit sales in the past decade. However, Ericsson's close ties to Sauber owners Longbow Finance appear to have edged it.
Ericsson has been with the team since 2015, after an initial season with the now-defunct Caterham squad.More news: Guardiola regrets Redmond rant after City victory
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Giovinazzi, who served as Ferrari's third driver in 2017, has two Sauber race outings to his name, the Italian having stood in for the injured Wehrlein at this season's two opening rounds, with a best finish of 12th in Australia.
Despite scoring all five of the team's points for Sauber this season, Wehrlein now only has Williams as an option in F1 for 2018, with the Mercedes youngster facing a potential return to DTM.
Since the departure of former team principal Monisha Kaltenborn, Sauber has increasingly positioned itself as a Ferrari satellite team.
Marchionne, who is also chairman of Sauber's engine suppliers Ferrari, has made the title sponsorship of Sauber part of his reshaping of the FCA-owned Alfa Romeo brand. That was promptly followed by a deal with Ferrari for 2018.