ALLEN PARK - The Detroit Lions' running back battle just heated up.

With rookie Mikel Leshoure lost for the season with a torn left Achilles tendon, the Lions signed free agent running backs Mike Bell and Jerome Harrison. Interestingly, Bell and Harrison were traded for each other last year in a swap that involved the Cleveland Browns and Philadelphia Eagles.

Bell played for the Eagles early in the season, appearing in four games and running for 28 yards on 16 yards (1.8-yard average). Meanwhile, Harrison played in three games for the Browns, rushing 31 times for 91 yards for a 2.9-yard average.

During the season the two running backs flip-flopped teams. Bell played in nine games with the Browns and had 31 carries for 71 yards (2.3-yard average) while Harrison appeared in seven games with the Eagles, rushing 40 times for 239 yards (a 6.0-yard average).

Both players had good seasons in 2009. Bell, who had 677 yards in his rookie season with the Broncos in 2006, had 654 yards with the Saints, averaging 3.8 yards per carry. Harrison had 862 rushing yards, five touchdowns and a 4.4-yard average in 2009 with the Browns.

Both players are 28 years old while Bell (6-0, 215) is more of a one-cut runner while Harrison (5-9, 195) runs with more power.

The Lions will start Jahvid Best but now the other two backup positions are in question. Those two spots have four guys fighting for them - Bell, Harrison, Maurice Morris and Aaron Brown.

To make room for the two new running backs, the Lions waived tight end Preston Dial and placed Maurice Leggett on the waived/injured list. Leshoure has not yet been officially placed on the injured reserve list.