At least five defensive players with multiple starts this season for the Bears will be unavailable Sunday against the Baltimore Ravens. Six if defensive end Shea McClellin is out, which appears likely.
McClellin did not practice Wednesday and hasn't since last Thursday when he suffered a hamstring injury in practice just three days after his career-best 3-sack game at Green Bay.
Linebacker Lance Briggs (fractured shoulder) won't play, defensive tackles Henry Melton and Nate Collins are finished for the season with knee injuries, and cornerback Charles Tillman also is on injured reserve but designated to return, although not until the postseason.
The defense has sunk to the bottom quarter of the league in almost every pertinent statistical category, so the Bears would seem to have plenty to complain about. But they aren't. They continue to plug new players in and expect them to step up -- even though they have yet to hold a team to fewer than 20 points.
"You don't make excuses about it," coach Marc Trestman said. "(The backups) are here because they're expected to play. We're expected to develop players and coach them, and that's what we're doing in a demanding and passionate way to get them ready to play.
"This is going on throughout the National Football League. We're in the middle of the season and things happen. We embrace the opportunity to get them ready. I know they're excited to be a part of it."
Zack Bowman, Tillman's backup and one of the Bears' top special-teams players, is the latest to be promoted because of an injury. He has started 17 games for the Bears but just two since the 2011 season, although one of them was in Week 6 against the New York Giants when Tillman was out with a knee injury. In that game Bowman picked off his first pass since 2009.
"The big thing I learned from (Tillman) is to just go out there and play football and have fun," said the six-year veteran. "There's just a lot more plays out there on defense than there is on special teams."
The 6-foot-1, 196-pound Bowman already has played 136 defensive snaps this season because of Tillman's balky knee, so it's not as if he's coming in totally untested.
"We have a tremendous amount of confidence in Zack to get the job done," defensive coordinator Mel Tucker said. "He's a veteran player. He's played in some games and done a good job when he's gone in.
"Obviously, you never want to lose a great player like Charles. But, unfortunately, injuries are a part of this game that we play and we coach, so it's next man up."
Fortunately for the Bears, they're facing a Ravens offense that bears little resemblance to last year's Super Bowl champions. Running back Ray Rice is having by far the worst season of an excellent career behind a disappointing line that also has failed to provide adequate protection for Super Bowl XLVII MVP Joe Flacco.
The Ravens are last in average gain per rush, 30th in rushing yards, 23rd in sacks allowed and 29th in total yards. Flacco's passer rating of 77.3 is 25th in the league.
All things considered, the Bears' defense has shown some improvement, allowing a total of 41 points in the last two games after permitting an average of 29.4 in the first seven. Trestman credits Tucker for persevering throughout an injury-plagued 10 weeks.
"Mel's done an amazing job, in my opinion," Trestman said. "He's been consistent with the guys in terms of his passion, the way he's teaching. He's a positive guy. I thought our defense played well enough (in the 21-19 loss Sunday to Detroit) for us to win under unusual circumstances of having so many players out.
"Are we where we want to be? No. We're always trying to get better. But he's done an outstanding job in the classroom. On the field he's excellent, and he's done a great job of managing the team for the last couple of games on the field. It's very impressive to watch."
• Follow Bob's NFL and Bears reports on Twitter @BobLeGere.