Isaac Sopoaga has been the man in the middle of the 49ers defense for a long time.
At 6-foot-2 and 330 pounds, No. 90 is hard to miss, a huge but agile hulk lined up across from the opposing center as the nose tackle in San Francisco’s 3-4 defense.
The eighth-round pick out of Hawaii in 2004 has been a key component in the Niners’ defensive formula, plugging holes and occupying blockers on the line between defensive ends Ray McDonald and Justin Smith.
“He’s the No. 1 run-stopper," Pro Bowl safety Donte Whitner said in the week leading up to the Super Bowl. “Anyone who takes on two guys who are 300-plus pounds on each and every snap, he’s the rock of your defense. You can look at a lot of defenses around the National Football League and they don’t have that.
“In the 3-4, you don’t have a great defense if you don’t have a great nose tackle.”
This offseason, the 49ers must decide how much it’s worth to them to keep Sopoaga as “the rock” in that defensive line.
Sopoaga is one of a handful of unrestricted free agents on the team, a group that includes tight end Delanie Walker, safety Dashon Goldson and wideout Randy Moss.
The 49ers enter the offseason below the salary cap, but will need to spend their dollars wisely. Not every free agent will be retained, and Goldson appears to be the priority.
Sopoaga, 31, made $3.8 million in 2012, and the San Francisco Chronicle’s Eric Branch believes that if the 49ers retain their nose tackle, “It will be at a drastically reduced salary.”
Why? According to Branch, citing Pro Football Focus, Sopoaga played just 31 percent of defensive snaps in 2012, because the 49ers were forced to use nickel and dime schemes when opposing teams went into multiple-receiver sets. And, when Sopoaga was on the field, he wasn’t as statistically productive as in the past, Branch wrote, noting he ranked 82nd among 85 nose tackles and defensive tackles.
This past season, Sopoaga had 27 total tackles with one sack. But much of what he does can’t be measured statistically. Sopoaga always has been able to tie up blockers to allow the team’s linebackers to make plays.
Yet the 49ers may believe they can go to a cheaper and younger option in Ricky Jean Francois, 26, another free agent who served as a backup in 2012. Francois made just $615,000 in 2012 so, even with a raise, could save the 49ers some salary cap space. If the 49ers retain Francois, wrote Branch, Sopoaga’s tenure in San Francisco may be at an end.
“If Sopoaga is back for a 10th season with the 49ers, it will be at a drastically reduced salary,” wrote Branch. “His future with the team also figures to hinge on on the free-agent status of his backup, Ricky Jean Francois.”
Yet a financial gain might prove to be a loss in chemistry and on-field performance. Recently, 49ers defensive coordinator Vic Fangio praised Sopoaga as a reason the 49ers have been such a strong defensive team.
It’s chemistry as much as biology, he said.
“Isaac’s just a fun-loving guy,” Fangio told 49ers.com. “Everyone loves being around him. He’s just a key part to our defense, both from a tangible standpoint in the way he plays the nose and the intangible standpoint, just being one of the guys.”