Ryan Mason said his West Brom side "didn't do enough" in their 3-0 defeat at Millwall.
Goals from Jake Cooper, Femi Azeez and Zak Sturge gave the Lions a huge victory at The Den.
They are now level on points with West Brom and Mason was very disappointed in the performance.
"Every aspect of the game we were probably outdone, which is tough to take," Mason told BBC Radio WM.
"We didn't assert ourselves or show enough quality and personality.
"I need to work that and get more out of the lads.