The midfield pair have suffered injury-hit seasons, with Morrison battling an Achilles problem, which has sidelined him since September, and Chadli struggling to overcome a hip issue.
Kieran Gibbs could also be missing with a muscle injury and will need to pass a late fitness test.
Evans (foot), Craig Dawson (fatigue) and winger Matt Phillips (hamstring) are fit to face the Seagulls on Saturday after sitting out the 2-0 FA Cup win at Exeter.
Having picked up his first win in charge in Devon last week, Pardew has called on the West Brom faithful to get behind the team as they seek a much-needed three points.
He said: “We’ve had some tough games at home since I’ve been here. This is a game where maybe our fans would come expecting to win.
“In the circumstances we really need them. If the fans are anything like how they were for the Arsenal game, I’ll settle for that.
“If we are going to get out of this we are going to need our 12th man.”
Provisional squad: Foster, Myhill, Palmer, Hegazi, McAuley, Dawson, Evans, Nyom, Gibbs, Brunt, Field, Livermore, Krychowiak, Barry, Burke, Yacob, McClean, Phillips, Robson-Kanu, Rondon, Rodriguez, Leko.