The Yankees are going to be without their ace for at least the first month of the season.
Severino, 25, is still in the midst of his two-week shutdown period after feeling soreness in his shoulder and would have to start his throwing from scratch once he resumes.
The righthander had an MRI earlier this month but it did not reveal any structural damage but he also has not had a Spring Training start.
Severino said everything is on schedule and he will resume playing catch next week.
"I just want to be healthy and help my team," he said.
Luis Cessa has pitched well this spring and could be the likely spot starter for Severino.
Meanwhile, Cashman does not believe outfielder Aaron Hicks will be ready by Opening Day.
Hicks, 30, has been sidelined with a lingering back issue and it is realistic the center fielder will start the season on the injured list.
Cashman expects Hicks will be healthy by March 28 but will need more at-bats and work before he can join the team.
Hicks' absence could open the door for both Greg Bird and Luke Voit to start the season with the team. It also could help Clint Frazier's odds, although he has struggled at the plate this spring and could lose out to a spot to utility man Tyler Wade.
As for CC Sabathia, who started his Spring Training work late after a heart procedure, Cashman expects a return in mid-April after he serves a five-game suspension stemming from an incident last season.
The Yankees extended both Severino and Hicks earlier this spring. Severino signed a four-year, $40 million extension while Hicks inked a seven-year, $70 million extension.