SAN FRANCISCO -- Outside linebacker Aldon Smith was placed on the 49ers' reserve/non-football-injury list Monday as he entered treatment after his recent drunken-driving arrest.
Smith's timetable for returning is undetermined, but it might be a month, ESPN first reported. He can be activated by the 49ers at their discretion. According to a league spokesman, there is no minimum length of time that he has to be out.
Also unknown was Smith's destination for treatment. He reportedly was flying to a rehabilitation center Monday morning, according to ProFootballTalk.com, but coach Jim Harbaugh declined to confirm that.
In a team-issued statement, Smith said: "I am taking a leave of absence to address my health. I am sorry that I have affected my team, my family and the organization. I will do everything in my power to handle this situation the best way possible. I appreciate the support of the 49ers and our fans."
Harbaugh also declined Monday to "rehash" the 49ers' decision to play Smith in Sunday's 27-7 loss to the Indianapolis Colts.
"We're supportive of Aldon, as we are of all players, all of our coaches, our personnel. Always supportive of in-house," Harbaugh said. "We've hashed through it and now taken steps, and Aldon's taken steps. We support him in that."
General manager Trent Baalke said in a statement: "Aldon Smith is taking a leave of absence to address a personal matter. The 49ers organization both respects and supports Aldon's decision and commends him for taking responsibility for his actions."
Smith still likely faces a suspension from the NFL, which has not commented on Friday's arrest. Such discipline might be delayed until Smith's criminal case is resolved, however. His arraignment is Nov. 4.
The 49ers have not yet decided whether to dock Smith's pay, according to a source who noted such a move might depend on potential fines the NFL imposes on him. Smith has a base salary of $1.68 million this season.
The 49ers likely will use a committee of defenders to fill in at right outside linebacker and right defensive end for Smith, who played all 72 defensive snaps Sunday. Three players stand out as likely replacements:
"There's adversity. There's an opportunity to stare it in the face and whip it," Harbaugh said.
Smith had no sacks Sunday against the Colts.
New to the injury report: running back Frank Gore (knee), right tackle Anthony Davis (shoulder), center Jonathan Goodwin (elbow), wideout Kyle Williams (rib) and cornerback Carlos Rogers (knee). Quarterback Colin Kaepernick no longer is listed with a foot injury, nor is running back LaMichael James (knee).
Staff writer Tim Kawakami contributed to this report.