Hillenmeyer didn't make the trip for the Bears' preseason finale Thursday night against the Cleveland Browns. Bears coach Lovie Smith initially expected Hillenmeyer to be available.
It's likely that reserve Kevin Malast will start in his place because starter Brian Urlacher, who strained his left calf against the Oakland Raiders earlier in the preseason, isn't expected to play until the Sept. 12 opener against the Detroit Lions.
Defensive coordinator Rod Marinelli said he's thankful for the club's depth at linebacker.
"We're very fortunate," he said. "We've got five starters sitting there. And another -- No. 62 [Brian Iwuh] -- is coming along. At least he's shown that in the preseason. So we feel good about that."
Iwuh will start in place of Lance Briggs (ankle) at weakside linebacker.
Michael C. Wright covers the Bears for ESPNChicago.com and ESPN 1000.