Mitch Wishnowsky experienced a back issue during Sunday's game against the Tampa Bay Buccaneers. Head coach Kyle Shanahan described it as a "flare-up" and noted that the team will assess the punter's condition and consider treatment options as the week progresses.
While the addition of O'Donnell could be precautionary, it may also indicate concerns that Wishnowsky could miss time.
O'Donnell was drafted by the Chicago Bears in the sixth round out of Miami (FL) in 2014.