NFL Media Insider Ian Rapoport reported Sunday that Aldon Smith would be placed on the non-football injury list as soon as the San Francisco 49ers linebacker registered at a treatment facility.

The 49ers made the transaction official Monday. A team source confirmed to Rapoport that Smith has indeed checked into rehab as he was ineligible to be placed on NFI until he did so. Rapoport reports per a team source that Smith is expected to miss a month or so. The team only will bring him back when the doctors clear him.

There is no minimum amount of time that Smith must stay on the NFI list. He can be activated as soon as he's deemed ready. The 49ers do not have to pay Smith his salary while he's on the NFI list. Rapoport notes it's uncertain if they will.

"Aldon Smith is taking a leave of absence to address a personal matter" general manager Trent Baalke said in a statement. "The 49ers' organization both respects and supports Aldon's decision and commends him for taking responsibility for his actions. The long-term well-being of our players is paramount and we will stand by Aldon as he works toward addressing this issue."