The Brighton winger, who was carried off in last Saturday’s 2-1 defeat at Manchester City, has suffered an “important” injury, manager Roberto De Zerbi confirmed.
Teammate Danny Welbeck also hobbled off with a hamstring problem which De Zerbi confirmed was serious.
Asked if March would play again this season, the Italian said: “I don’t know. It is difficult to fix a time.
“For sure it is a long period. I don’t know how many months.
“Solly unfortunately is a very tough injury, very important injury.
“We will lose him for a long time and Welbeck is the same, both long term.
“We love Solly and we will be very close with him to support him every day.
“But we have to accept it because football is like this. Injuries can happen, it can happen to lose a season. It is football.”
De Zerbi is already without left-back Pervis Estupinian, Julio Enciso and full-back Tariq Lamptey as Brighton prepare to host Ajax in the Europa League on Thursday night.
He added: “I don’t want to cry because sometimes coaches cry when they lose players.
“We have to move on and work harder to find a different solution.”