Vance McDonald (hip) and Garrett Celek (back), both tight ends, were listed as questionable on the team's injury report on Friday. That left the 49ers with Blake Bell as the only healthy tight end. Eric Branch of the San Francisco Chronicle reports that McDonald "presumably" will not play on Sunday against the Dallas Cowboys.
In order to make room on the roster, the team has released RB DuJuan Harris.
Hamm originally joined the 49ers after the team claimed him off of waivers from the Washington Redskins in December. He was released during the team's final roster cuts and then signed to the practice squad the following day.
Harris was re-signed by the team on September 13, following his release the day before.