Albion midfielder Andrea Orlandi has been ruled out for up to six weeks by a broken rib.
The extent of the damage suffered by the Spaniard during Saturday’s 3-0 defeat at Crystal Palace has now been confirmed.
It is a major setback for the Seagulls. They have plenty of midfielders to choose from but Orlandi has become increasingly influential since signing from Swansea at the end of the transfer window, including scoring his first goal in the home victory against Bristol City last week.
Boss Gus Poyet told The Argus: “He has got a broken rib and he is going to be out for a while. It is going to be four to six weeks, depending on the healing process for Andrea.
“He didn’t play a lot at Swansea, so we have tried to keep an eye on him because of the football he has missed in the past.
“Everything we have done until now is going to be gone. In a month-and-a-half we will have to start from zero with him, so it is very unfortunate and then, of course, there’s his quality as well.
“He has been getting more influential in the team and also with set plays, so it’s a blow but that is why the squad is there, to make sure we don’t miss him too much.”
Fellow Spaniard Bruno has also been troubled by a rib problem but the damage is less serious and Poyet expects to have the right-back available for Saturday's trip to Charlton.
Poyet also remains hopeful about the prospects of Wayne Bridge (calf) and Adam El-Abd (hamstring) returning against Charlton to ease a defensive crisis. Marcos Painter (calf) is already ruled out and Lewis Dunk is banned for one game for his early red card at Palace.
Poyet said: "I really hope they (Bridge and El-Abd) are going to be allright. At least one of them, I'd take that right now."