Sauber boss Frédéric Vasseur believes the Swiss outfit was impacted by a weak chassis last season rather than by its old-spec Ferrari engine.
The Hinwil squad raced with a year-old Ferrari power unit in 2017 and often invoked the engine's under-performance to justify a low-profile season in which it was the only team not to score a single championship point.
Vasseur, who was named as team boss last summer, says an honest assessment of Sauber's performance revealed a bigger problem on the aerodynamic front.
"We have to honest with ourselves," he told Autosport.
"The biggest issue wasn't the engine. The engine was 2016, but the handicap was only a couple of tenths.
"If you compare with the other teams, the biggest issue was on the chassis side, and we have to be focused on this and push like hell on the aero."
Sauber extended its contract with Ferrari for 2018, inheriting an Alfa Romeo commercial partnership and, more importantly, a new-spec engine.
"At least you will remove the engine from being a preoccupation," Vasseur added.
With an upgraded power unit, intense focus on chassis design and the recruitment of the highly rated Charles Leclerc, Sauber is undoubtedly facing brighter prospects this year, insists the Frenchman.
"Now we have a brand new project. Sauber started very late last year, but the 2018 project is on schedule," he says.
"But of course only the first test in Barcelona at the end of February will tell us where we are."