FA Cup elimination to Reading means the Baggies can now focus on league survival.
But Morrison warns: "We are on a slippery slope. That wasn't us out there and we are disappointed.
"We hadn't won in five before this and we are struggling in the league so yes, confidence is low, it's got to be.
"We played a strong-ish team, but the lads have played four games in eight days now and we felt it.
"It's up to the manager to keep our spirits high. Obviously they are not now because we've just got beaten again.
"We wanted to get back on the winning track, but it wasn't to be. We've got to get back to what we were trying to do at the start of the season."