The Detroit Lions made their first surprise move of cut week, releasing running back Zach Zenner on Tuesday.

Zenner played in eight games and made one start last year after Kerryon Johnson was lost to a season-ending knee injury. He played as the Lions' No. 4 running back for most of this preseason, behind Johnson, C.J. Anderson and rookie Ty Johnson, but seemed to be in line to make the 53-man roster because of his special-teams ability.

With Zenner gone, and with injury concerns at linebacker (Jarrad Davis) and on the offensive and defensive lines (Frank Ragnow and Da'Shawn Hand), the Lions likely will keep three running backs on their initial 53-man roster.

[ Birkett's final Lions roster prediction: Tough decisions on defense await ]

Kerryon Johnson, who led all NFL running backs in yards per carry last season, is the unquestioned starter, with Anderson his primary backup.

Mark Thompson, who leads the Lions with 80 yards rushing and two touchdowns on 17 carries this preseason, is a candidate for the practice squad.

Zenner originally signed with the Lions as an undrafted free agent out of South Dakota State in 2015.

He was a fan favorite who led the Lions with 183 yards rushing that preseason, and appeared in 36 games over the past four seasons, mostly as a backup.

Zenner had a career-high 93 yards on 21 carries in the Lions' season-ending win over the Green Bay Packers last season. He signed a one-year deal to stay in Detroit this spring.

The Lions have until 4 p.m. Saturday to trim another 36 players from their 90-man roster.

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Contact Dave Birkett at dbirkett@freepress.com. Follow him on Twitter @davebirkett. Read more on the Detroit Lions and sign up for our Lions newsletter.