The Cardinals just signed running back Marlon Mack last week, his first practice -- in which he looked good -- coming in Saturday's Red & White Practice.

Just three days later, his season was over, and the Cardinals put him on Injured Reserve.

To replace Mack on the roster, the Cardinals signed Stevie Scott III, an Indiana product who most recently played with the USFL's Michigan Panthers.

Scott, who had 78 carries for 295 yards and a touchdown with the Panthers, has spent time with the Saints and Broncos.

Mack suffered a significant left Achilles injury in practice on Tuesday, a non-contact injury when he was flaring out for a pass without defenders. Mack knew it was a problem when it happened, and needed help to limp to the locker room unable to put weight on it. It is the second time in Mack's career he has torn his Achilles, after the same thing happened early in the 2020 season.

Mack tore his right Achilles when he was with the Colts.

Scott joins a backfield with questions. James Conner is the starter and Corey Clement has gotten most of the No. 2 snaps in camp with Keaontay Ingram having done little with an undisclosed injury. The running back room also includes Ty'Son Williams and Emari Demercado.

"We'll always try and do what's best for the team," coach Jonathan Gannon said.

The Cardinals open the preseason Friday night at home against the Broncos.