The 49ers officially signed defensive end Jaylon Allen to a one-year deal today, placing DL Tarron Jackson on injured reserve following his neck injury.

The San Francisco 49ers held their breath toward the end of practice on Sunday when defensive lineman Tarron Jackson collapsed on the field, according to NBC Sports Bay Area. Jackson was taken off the field on a stretcher and transported to the hospital for further evaluation.

San Francisco placed defensive lineman Tarron Jackson on the Injured Reserve List, two days after he suffered a neck injury in a team practice. In a corresponding transaction, the team signed defensive lineman Jaylon Allen, most recently of the United Football League’s Memphis Showboats, to a one-year contract.