Tony Pulis says Albion need to be more consistent after the Baggies were thumped at Crystal Palace.
The hosts dominated the game and deservedly took the lead in the 78th minute when Yannick Bolaise headed home from close range.
Yohan Cabeye then scored a late penalty after Chris Brunt had fouled the lively Wilfried Zaha.
The Baggies managed only one effort on target against the Eagles and looked devoid on any attacking threat.
Pulis admits Albion's performance was a surprises after the same side played so well against Villa on their last away appearance.
"You can't believe it was the same team that played against Aston Villa, they played so well there and this performance was like chalk and cheese.
"They were much better than us.
"How do you legislate for it? I don’t know if it was confidence or whatever. But we’ve got to sort it out. We can’t go from a performance of eights and then drop down to threes and fours.
“I’m not picking on one person, that’s the group. They certainly weren’t on it.”