Berahino was left with a shiner after blows were exchanged between teammates following their 3-3 draw with Cardiff City.
The Daily Star says the player who punched him in the face at the weekend was Baggies midfielder Morrison.
Players rounded on the young striker who was guilty of giving away possession in the build up to Cardiff's stoppage time equaliser.
Morrison took exception afterwards when Berahino stood his ground in the dressing room.
An eyewitness said the two squared up with Morrison swinging and catching Berahino in the face.
Berahino is understood to have "got a couple of digs in" and attempted to get Morrison in a head lock before the brawl was broken up by team-mates.
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