"Justin's All-Pro contributions on the field, as well as his leadership on and off the field, are integral to our success," general manager Trent Baalke said Wednesday.
His off-the-field talents apparently include negotiating. NFL.com's Ian Rapoport reports that Smith handled the contract extension talks himself, a contract which Smith said likely will be his final NFL contract. He previously was represented by CAA.
Although the contract's financial numbers aren't in yet, this is a show of faith that Smith will return to dominant form after undergoing surgery to repair his partially torn triceps following the 49ers' loss to the Baltimore Ravens in Super Bowl XLVII.
Before J.J. Watt turned in the best season by a defensive lineman in NFL history, Smith was the league's premier 3-4 defensive end. His value to the 49ers was reinforced when edge rusher Aldon Smith failed to record a single sack over the final six games of the season -- without the benefit of a healthy Justin Smith running stunts to tie up offensive linemen.
Smith's extension ensures that the 49ers will have the six most valuable defensive players of their front seven locked up for the next two seasons.
Follow Chris Wesseling on Twitter @ChrisWesseling.