Top offseason needs: AFC West

Peyton Manning's presence means the Denver Broncos have far fewer holes to fill. Chris Humphreys/USA TODAY Sports

Welcome to the 2013 version of Insider's offseason staple series: Plugging the Holes. This marks the first of an eight-part examination in which Football Outsiders identifies the biggest needs for every NFL team, division by division, going into the 2013 offseason.

The series starts Monday with Outsiders' look at the AFC West.

Denver Broncos: Interior run defenders

After Keith Brooking replaced Joe Mays at middle linebacker in Week 6, the Broncos went from allowing 120.2 rushing yards per game to allowing 77.9 per game the rest of the way. Mays had been a solid downhill player, but in new coordinator Jack Del Rio's scheme he struggled to make pre-snap calls. Brooking stabilized Denver's base 3-4 as a stack linebacker and, surprisingly, held up well enough on the few occasions when he was asked to play in nickel.

That's the good news with Brooking; the bad news is he's a free agent who turns 38 in October. Prior to signing with Denver last August, he'd been showing noticeable decline since his mid-30s. History says that re-signing Brooking would be a roll of the dice on John Elway's part.