Smith had surgery on the thumb Thursday and hoped to shed a hard cast for a splint by next week, according to The Free Press.
Smith, who led the Lions in rushing in 2008 and 2009, missed the first three weeks of this season while on the mend from knee surgery.
As Smith's season was ending, Campbell's was just beginning.
At the time, Army policy would have allowed the West Point graduate to serve as a recruiter if he made the team. A subsequent Department of Defense policy superseded that 2005 Army policy, and Campbell was ordered to give up professional football for "full-time traditional military duties."
Campbell was released from his active duty obligations in May 2010 and joined the Lions' practice squad before the start of this season.
The Associated Press contributed to this report.