Florence, a 10-year NFL veteran, was cut by the Denver Broncos on Friday.
Florence signed a two-year deal with Denver in May after his release from Buffalo, but the Broncos kept just five cornerbacks when they trimmed their roster to 53. Tony Carter won the nickel back job and fourth-round draft pick Omar Bolden will be the dime back.
Asked why he kept Carter over Florence, Broncos boss John Elway said, "He played better. ... We just felt that Tony was a better football player."
Detroit has a glaring weakness is in its defensive backfield and had cut cornerback Alphonso Smith on Friday.
The Lions' weakness in the secondary was exposed in the Lions' last two games of the 2011 season, losses to Green Bay to close the regular season and New Orleans in the playoffs, when they gave up 946 yards passing and nine TDs. The situation got more bleak in the offseason when starting cornerback Eric Wright left for Tampa Bay as a free agent and his replacement, Aaron Berry, got cut for being arrested twice, and safety Louis Delmas needed knee surgery.
Detroit was desperate enough for help at cornerback that it was willing to give up a conditional draft pick to Washington for Kevin Barnes, a player the Redskins planned to release.
Florence had three interceptions last season, forced one fumble and was credited with 12 passes defensed. He has 17 career interceptions.
Information from The Associated Press was used in this report.