Olivier Giroud's powerful 14th-minute header consigned Pepe Mel's side to another reverse in what has been a difficult campaign for the Midlands outfit.
Albion sit 16th in the table and, although it seems likely they will secure top-flight football for a fifth consecutive term, Brunt was scathing in his appraisal of how 2013-14 has turned out for the club.
"Even if we are safe we will be bitterly disappointed with a poor season," he is quoted as saying by BBC Sport.
"It has been a bit of a shambles on and off the field.
"If we do not learn from this season, we will not learn from anything."
West Brom have won only seven league games this season - giving them the joint-lowest tally of victories in the division together with relegated Cardiff City.
