Fabian Hurzeler admitted Albion will have to learn from their mistakes after losing for the first time this season.
Cole Palmer scored four first-half goals as Chelsea won 4-2 at Stamford Bridge, despite first Premier League goals for Georginio Rutter and Carlos Baleba.
“I think we had a good start and controlled possession. We scored one and afterwards we had too many individual mistakes and if you do that you can’t win,” he said.
“We should quickly learn from this and try to control the game better without these easy give-aways of the ball.
“In possession it was good but to win you need to be good in both phases and we didn’t defend how we wanted to. It was too easy for Chelsea to break our lines. They took advantage and have the individual quality to do it. But we have to defend better individually and we have to learn quickly.
“If you lose you can’t say there are big positive things about the performance but of course we try to analyse the game, adapt small things and see there were also big chances for us in the game.
“Every time we made a mistake Cole Palmer punished it. We have to be honest to ourselves – we didn’t deserve to win.”