San Francisco made the move Saturday, ahead of Sunday's NFC West game at Arizona.
The 49ers made the move to clear roster room for tight end Asante Cleveland to be moved to the active roster from the practice squad. Starting tight end Vernon Davis and backup Vance McDonald both have injuries and it was unclear whether either would play against the Cardinals.
Johnson, who played for coach Jim Harbaugh in college at San Diego, signed with the 49ers on May 14.
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