Justin Smith contract extension a boon for Aldon Smith, 49ers

Justin Smith (94) and Aldon Smith form one of the league's most feared duos. (Kevin Terrell, AP) Were the diminished returns in Aldon Smith's game late last

Justin Smith (94) and Aldon Smith form one of the league's most feared duos. (Kevin Terrell, AP)

Were the diminished returns in Aldon Smith's game late last season caused by Justin Smith's absence due to injury? The timing of those two occurrences appeared to be much more than coincidence. And rather than risk having to permanently worry about Aldon Smith's performance sans his defensive counterpart, the 49ers locked up Justin Smith through 2015 with a two-year contract extension.

There were plenty of other reasons for San Francisco to deliver Smith an extension, mind you, from his four consecutive Pro Bowls to the money it figures to save the team in 2013 (Smith was set to make $7.5 million this year).

But for as talented as the individual pieces of the 49ers' defense are, much of that unit's recent success has come because the players involved fit very specific and structured roles. That's why, for example, the 49ers were lit up by Seattle with Smith out of the lineup in Week 16 last season, despite Ricky Jean-Francois holding his own as a replacement.

Smith has continued to play at an extremely high level, too. While his streak of 165 consecutive starts was broken last season, the soon-to-be 34-year-old defensive lineman has averaged more than six sacks per year since coming to the 49ers in 2008.

"Justin’s All-Pro contributions on the field, as well as his leadership on and off the field, are integral to our success as a team," GM Trent Baalke said in a statement.

San Francisco has not hesitated to build its defense partially around him, either. Smith's presence on the line plus the combo of NaVorro Bowman and Patrick Willis at inside linebacker keys the 49ers' 3-4, freeing up players like Aldon Smith and Ahmad Brooks to play with unbridled aggressiveness.

There's also a definite benefit for both Justin Smith and the 49ers to take care of this contract situation now (beyond immediate help for the cap), rather than wait until Smith reached the verge of free agency next offseason. Assuming Smith remains his durable, productive self, he should be able to stay a valuable contributor on the defense. And he no doubt would have drawn substantial interest had he reached free agency.