San Francisco 49ers defensive coordinator Jim O'Neil spoke to the media today and shared his thoughts on the team losing the heart of the defense – ILB NaVorro Bowman. Bowman suffered a season ending torn Achilles in the 49ers' loss to the Dallas Cowboys on Sunday.

"As far as NaVorro, its' obviously a huge loss for our defense," O'Neil said. "Any defense would miss his playmaking ability, his presence on the football field. We're confident in the guys in that room to be able to step up, but I still see NaVorro being a big part of what we do here as far as his leadership abilities in the classroom with the guys and then his presence in the locker room. So he'll continue to take that role for us off the field, but he's a guy that we'll definitely miss on the field."

Who takes over the leadership role for Bowman? Who will now be the spirit of the defense? "I think Antoine Bethea is one of those guys," O'Neil answered in response to that question. "I think Quinton Dial is one of those guys in the trenches. So those were the first two that kind of jumped off for me."

Nick Bellore has been a name that has been thrown around as the player to potentially replace Bowman. Bellore is the linebacker that came in for Bowman following his injury against Dallas. O'Neil didn't want to commit to Bellore being the automatic replacement at Bowman's spot. "We'll kind of see how practice goes, but like I've said several times, if you're on the 53, we're going to need you," he said. "So it will be between Nick, Mike Wilhoite, Gerald Hodges, and Shayne Skov."

On Sunday, Bowman went down while rushing the line of scrimmage and immediate grabbed at his left ankle. He received attention from the 49ers' medical staff and eventually walked off of the field with a limp and some help from team trainers. Bowman was later carted to the team's locker room. An MRI on Monday revealed the severity of the injury.

Through nearly four games, Bowman had 35 tackles, a sack, an interception, a forced fumble, and two passes defended. Last season, he was in on 1,126 defensive snaps. 627 of those were against the pass while 499 were against the run. During that time, Bowman compiled 154 tackles – which led the league – 2.5 sacks, and two passes defended.

Through four games this season, Bowman was the team's highest rated player according to advanced statistics site Pro Football Focus.