Lance Stroll will be replaced by Aston Martin reserve driver Felipe Drugovich if the Canadian is not fit enough to race in the Bahrain Grand Prix.
Team principal Mike Krack had refused to rule out the possibility of Sebastian Vettel making a shock return from retirement to fill in for Stroll.
But on Sunday the team said Drugovich would race if Stroll does not recover from injury before next weekend.
The 22-year-old Brazilian drove the car in pre-season testing this week.
Stroll injured his wrist in what the team described as a "minor" cycling accident last week and was forced to sit out the three days of pre-season testing on Thursday, Friday and Saturday.
He is due to try driving in the team's simulator as a first step to evaluating whether he will be able to compete in Bahrain on 3-5 March.
Aston Martin said: "The team will continue to give Lance every chance to race, pending recovery from his injury. Should he not be fit to compete, then Felipe will drive the AMR23 alongside Fernando Alonso."
