When needing a yard for a first down, touchdown or two-point conversion, the NFC North side were successful from 18 of their 26 attempts in the first seven games of the season, but that has fallen to six from 17 in their last five outings.
The head coach told the team's official website: "It really has come down, with all due respect to our opponents, more about us than them. It's simply the execution of the play. It's everybody doing their job.
"We just haven't executed plays completely with all five, six, seven, eight guys, whoever is involved. There's no one guy. It's been a bit of taking turns.
"We've spent time on it and extra time this week in our walkthroughs and repeating plays and things like that to make sure everybody knows what to do."
The Bears host the Dallas Cowboys tomorrow.