The Detroit Lions' backfield reinforcement plan hit a snag before it ever got started. Detroit placed running back Isiah Pacheco on injured reserve on Tuesday, ruling out the former Kansas City Chiefs standout for at least the first four games of the 2026 season, NBC Sports' Pro Football Talk reported.

Pacheco battled a sprained MCL for much of training camp, but head coach Dan Campbell made clear a back injury that flared up late in camp is now the bigger concern. Campbell had spent the past week hedging on whether the 27-year-old would be ready for Week 1, saying he couldn't offer anything "definitive" — Tuesday's roster move answered the question for him.

A costly delay for Detroit's backfield plans

The Lions signed Pacheco to a one-year, $1.81 million deal this offseason, betting that a change of scenery would pay off after four seasons in Kansas City. There, he rushed for 2,537 yards and 14 touchdowns and won two Super Bowl rings, per ClutchPoints. The move made sense on paper: Detroit had just shipped veteran David Montgomery to Houston and needed a proven complement to star Jahmyr Gibbs.

Instead, Pacheco will watch at least the opening month from the sideline. With Detroit carrying five running backs on its roster, Jacob Saylors now slides into the primary backup role behind Gibbs, with Sione Vaki and Jabari Small also in the mix. The Lions used Pacheco's open spot to bring back tight end Tyler Conklin, while adding guard Elijah Klein and receiver Dominic Lovett to the practice squad, according to ClutchPoints.

Pacheco's four-game absence covers the entirety of Detroit's opening stretch, meaning the offseason addition won't suit up for the Lions until at least Week 5.

It's a familiar type of setback for Pacheco, whose physical, downhill running style helped define Kansas City's championship offenses but has also come with a history of camp and in-season injuries, including a concussion and a prior MCL issue during his Chiefs tenure. The Lions were counting on that same bruising style to spell Gibbs and keep Detroit's ground game humming deep into games.

For now, Campbell's staff will lean on the group behind Gibbs to hold the fort. Saylors, an undrafted find who impressed in camp, gets the clearest opportunity to carve out early-season touches, while Detroit waits on updates about Pacheco's back and a clearer target for his return.

The setback doesn't change Detroit's status as a projected NFC contender, but it does strip away one of the roster's more intriguing offseason bets right as the games start to count. The Lions will provide further updates on Pacheco's recovery timeline as the season progresses.