"We have things to work on. We're disappointed by the performance and result," he told BBC Radio Lancashire.
"There is much more quality in the team than we were able to produce. That is something we have to work on."
The former Blackburn centre-back has already stated his aim this season is an immediate return to the Premier League, but was not impressed with what he saw on Saturday.
"Defensively we were giving them too much space in between our lines. They had two good wingers but they were getting in way too many crosses," Berg added.
"Going forward we didn't use the ball as we should have done. We should have been taking more care with the ball as we were losing it too easily.
"We would like to be much better than this, and we should be."