A day after losing rookie running back Mikel Leshoure for the season, the Detroit Lions have picked up two new running backs.

The Lions announced this morning that they have signed Mike Bell and Jerome Harrison.

Both Bell and Harrison are 28-year-olds entering their sixth NFL seasons, and the two of them were actually traded for each other last year, with Harrison going from Cleveland to Philadelphia in exchange for Bell.

Bell’s best NFL season was his rookie year with the Broncos in 2006. He joined the team as an undrafted free agent and surprisingly was proclaimed the best running back in training camp by coach Mike Shanahan, and he ended his rookie year with 157 carries for 677 yards and eight touchdowns. Since then, however, he’s bounced around the league and only been productive at one stop, in New Orleans in 2009.

Harrison had a great college career at Washington State and was selected by the Browns in the fifth round of the 2006 NFL draft. He was mostly a role player in Cleveland, but he briefly emerged as a workhorse at the end of the 2009 season, with an incredible 106 carries for 561 yards and five touchdowns in the Browns’ last three games.

In 2010 Harrison lost his starting job to Peyton Hillis and was an afterthought in Cleveland, but after the Browns traded him to the Eagles he had a couple of solid games, carrying 11 times for 109 yards against the Redskins and 21 times for 99 yards against the Cowboys.

Jahvid Best is the Lions’ No. 1 running back, but there’s a good chance that both Bell and Harrison will make the Lions’ roster as backups.