The Saints failed to match their opponents at New Craven Park as they slumped to their fourth loss of the season.
"I could tell by the first few sets that we weren't quite there," Brown told Sky Sports News.
"Our kicking game was really poor and while our goalline was great, our defence elsewhere wasn't.
"There wasn't a lot we did well. But to hold them out and stay in the game was good but there was a lot we didn't do well."
The defeat has left St Helens in sixth place in the Super League table.