Midfielder Beram Kayal could return after more than three months out but defenders Sebastian Pocognoli (thigh) and Liam Rosenior (ankle) are out.
MK Dons, 18th in League One, have defender George Baldock available after hamstring trouble.
Top scorer Dean Bowditch (calf) remains sidelined along with Scott Wootton.
The Dons reached the fourth round of the FA Cup last season, eventually losing 5-1 to Chelsea.
Brighton boss Chris Hughton told BBC Sussex:
"We will use the squad. It is quite difficult to speak about the values of the FA Cup, as it is the way the game is these days.
"There is no doubt our focus is the league, as it is with many other clubs.
"It is a competition we want to go through in, because of the history, as it gives us more games. It will be a tough challenge as they have players who have played in the Championship and they will raise their game."
Championship leaders Brighton are without suspended pair Lewis Dunk and Kazenga LuaLua, with Connor Goldson set to replace Dunk at centre-back.