While Urlacher isn't going to be locked up with a receiver in a one-on-one situation, he does keep an opposing running back from being viable targets out the backfield.
In the two games Urlacher missed members of the opposing backfield averaged 88 yards in receptions compared to just 44.6 yards with him in the lineup.
The difference in average per catch, at 10.4 yards without Urlacher and 9.5 with him, but the number of receptions per game is nearly double at 8.5 to 4.7.
A dump off pass to back becomes an easy outlet for a quarterback in trouble because Hunter Hillenmeyer can't cover the same amount of ground that Urlacher is able to.
This will quickly be evident in the team's first game without Urlacher.
Edgerrin James is one of the better receiving backs in the league. This year he has 30 receptions and the only season he didn't finish with at least 51 except for when he played in just six games in 2001 because of a knee injury.
Urlacher is also capable of getting to the quarterback on blitzes. He has four sacks this season, which ranks second on the team.
The Bears should be able to maintain without Urlacher, but the difference between he and Hillenmeyer will not only be in the big-play ability but in the details.