The Japan winger, who has lit up the Amex Stadium for much of the last two campaigns, has suffered a back injury which could leave him on the sidelines for three months.
He has already missed a chunk of the season due to an ankle injury and his participation in the Asia Cup.
Mitoma’s prolonged absence will be a big blow in the Seagulls’ quest for a top-six finish in the Premier League, their Europa League campaign – where they play Roma in the last 16 – and their FA Cup challenge, which continues at Wolves on Wednesday.
Boss Roberto De Zerbi said at a press conference to preview the trip to Molineux: “It’s a bad, bad situation.”

5. Joao Pedro - thigh
The Brazilian who has 19 goals this term has not featured since the 4-1 win against Palace. Roma on March 7 could be a target for his return Photo: Mike Hewitt

6. James Milner - thigh
The former Liverpool man has not played since the 4-0 loss at Luton. Fulham on March 2 could be possible Photo: GLYN KIRK

7. Jack Hinshelwood - foot
The impressive teenager has not played since scoring in the win against Palace. Could be out for the season. Photo: Mike Hewitt

8. Solly March - knee
Sustained a serious knee injury at Man City earlier this term and unlikely to feature again this campaign. Huge blow! Photo: Andrew Powell