Albion had defender Nathan Stanton sent off for a second yellow card 15 minutes from the end but rarely looked like surrendering a lead given to them by top scorer Calvin Zola and midfielder Lee Bell, whose fierce shot took a big deflection off Barker.
"It was just one of those days as far as we were concerned," Barker said. "We tried and tried but it just didn't work for us. We just didn't play very well.
"They had a lucky break with their second goal because I think the shot would have been closer to the corner flag until it hit me and went in. That's what happens sometimes when things don't work out for you.
"I think you've also got to give Burton credit as well because they battled, tackled and bullied us a little bit, which hasn't been the case in the run we've had.
"But if we lose only once every 15 games, I'll take that until the end of the season.
"We've got another game on Tuesday, so we've got to reorganise and make sure we bounce back with a win.
"Three days ago we were on fire and we'll be looking to get back to that form very quickly."