In a statement released through the NFL Players Association on Saturday, Smith said: "I apologize to my teammates, coaches, the entire 49ers organization and 49ers fans for not being able to contribute on the field for the next several weeks. Over the last year, I have learned a lot and I'm working hard to grow from my experiences.
"I want to thank my family and friends, my teammates, my union and the 49ers for supporting me during this process. I will be at work daily to participate in all permitted work activities, and to support my teammates, just as they have supported me."
The NFL announced Smith's suspension Friday. The league said in a statement Smith had violated its substance abuse and personal conduct policies.
Smith missed five games last season to undergo treatment at an in-patient facility following his DUI arrest Sept. 20. In November, he pleaded not guilty to three felony counts of illegal possession of an assault weapon, stemming from a June 2012 party at his home.
Smith also was arrested April 13 at Los Angeles International Airport for allegedly making a bomb threat. No charges were filed.