Allen originally joined the Bears last year, spending 12 of the first 15 weeks of the season on the practice squad before rushing for 48 yards on 15 carries in the final two games against the Packers and Vikings.
The Notre Dame product was waived during final cuts despite excelling in the preseason finale against the Browns, leading players on both teams in rushing with 83 yards on 16 carries and receiving with five receptions for 51 yards and one touchdown while also forcing a fumble on a punt return.
Allen lost out in the battle for the third running back position to Booker, who rushed for 81 yards on 15 carries and caught four passes for 16 yards against the Browns before exiting with a head injury in the fourth quarter.
Booker was unable to practice this week due to the injury and had been listed as questionable on the injury report for Sunday's season opener against the Colts.
Booker signed with the Bears in July after spending four NFL seasons with the Dolphins (2007), Eagles (2008) and Vikings (2010-11). Released by Philadelphia before the 2009 campaign, the 5-10, 201-pounder played for the Hartford Colonials in the United Football League in 2010.
Booker joined the Vikings late in the 2010 season and averaged 23.8 yards on 18 kickoff returns over the final four games. He then appeared in 15 contests last year, rushing for 52 yards on 13 carries, catching eight passes for 82 yards and averaging 23.7 yards on 19 kickoff returns.
Trahan spent the first 12 weeks of last season on the Bears practice squad before recording five special teams tackles in the final five games.