By Dan Durkin-

(CBS) Last season, the Bears were fortunate with health on the offensive side of the ball, but not as fortunate on defense. By Week 5, the Bears’ depth on the defensive line was decimated, and the cupboard was bare from both a talent and development perspective. The numbers that followed were historically bad and served as a wake-up call to both the personnel department and coaching staff.

This season, both sides of the ball have been hit hard by injuries, which is testing the depth of the roster as well as the coaching staff’s ability to get inexperienced players properly prepared to play. Teams are known to self-scout their tendencies on the field, but the Bears took a moment to reassess their methodologies as a staff.

On Thursday, coach Marc Trestman admitted the Bears weren’t good enough last season with developing the bottom of their roster, and they have a renewed focus this season to cure those ills.

“There’s a lot of teaching that’s going on here,” Trestman said. “During different hours of the day, not just during the regular hours in terms of getting guys ready to play and putting ourselves in a position that if we do lose a player that other guys are in position where they’re system-ready and they know enough to go in there and do the job. We’ve seen some of that, certainly, over the last couple weeks. As we’ve said, last year I think that, and I think that I said this, I didn’t feel that we and I didn’t do a good enough job working through our practices and developing our players to where if they had to get in the game that they would be better than they were.”

In three games, the Bears have played (for varying stretches) without 10 starters, five on offense (including little-used fullback Tony Fiammetta before he was cut) and five on defense. Four rookies on defense and two free agents on the offensive line have been counted upon to contribute in crucial moments of games, and they’ve come through. To be able to deal with that type of adversity both in the week leading up to and during the game is a proof that the Bears’ development plan is working, as inexperienced players have proved to be trustworthy.

For that, Trestman credited defensive coordinator Mel Tucker, offensive coordinator Aaron Kromer and special teams coordinator Joe DeCamillis.

“Mel and Aaron and our coaching staff, Joe – particularly these last few weeks, Joe – we spend a lot of time with these guys,” Trestman said. “We’ve got good, talented young players on our team. They’ve got to be developed within the system and understand the discipline that’s involved and how to keep their poise in chaos.”

Dan Durkin covers the Bears for CBSChicago.com and is a frequent contributor to 670 The Score. Follow him on Twitter at @djdurkin.