The team reported that NaVorro Bowman will miss the rest of the 2016 season after tearing his Achilles in the 24-17 loss to Dallas.
Bowman, who was injured with just over six minutes left in the third quarter, immediately grabbed his left leg after suffering the non-contact injury.
If you want an example of how important Bowman is to the 49ers defense, all you have to do is look at what Ezekiel Elliot did to the 49ers after Bowman left the game.
With Bowman out over the final 21 minutes of play, Elliot ran for 92 yards and a touchdown on 13 carries (7.1 yards per carry). On the other hand, during the first two and half quarters that Bowman was on the field, Elliott was only able to muster a total of 46 yards on 10 carries.
Niners offensive lineman Joe Staley admitted after the game that there's no way for the team to replace Bowman.
"It stinks. It's really, really bad," Staley said, via the Sacramento Bee. "NaVorro is a captain for us, one of our team leaders. We're going to have to have a guy step up. That's a huge role to fill. You can't really replace a guy like NaVorro, but we have to have guys step up and be ready to go."
The injury against the Cowboys marks the second time in four years that Bowman has suffered a major injury.
The injuries were so bad that Bowman was forced to sit out the entire 2014 season.
Bowman returned with a vengeance in 2015 though: Not only did he start all 16 games for the 49ers, but he led the NFL in tackles with 154. The linebacker was named first-team All-Pro in 2015, and was voted to his third career Pro Bowl.
The 49ers will be hoping the 28-year-old can return with the same vengeance in 2017. The Achilles injury comes just two months after Bowman was given a four-year contract extension that's expected to keep him with the 49ers until 2022.
Bowman has been in San Francisco since 2010, when the 49ers selected him in the third round of the NFL Draft.