Since the Bears hired Mel Tucker as their Defensive Coordinator, they haven't said much about the scheme they would run. While it's widely assumed they will stick with the 4-3 defense Tucker ran in Jacksonville, the scheme should depend on the personnel; and if they lose defensive tackle Henry Melton, it could mean a switch to a 3-4.
In his opening press conference, new head coach Marc Trestman would not comment on what scheme he'd run on offense, noting he would have to view film and find out what the players do best. It seems likely the same will apply for the defense, where Tucker has experience running both 3-4 and 4-3 defenses.
Tucker got his first coaching job at Michigan State with coach Nick Saban, a noted 3-4 defense guru. His first NFL job came on Romeo Crennel's staff in Cleveland, first as the defensive backs coach, then as the defensive coordinator for his 3-4 scheme.
In the current pass-happy NFL, teams put a premium on pass rushers and Melton is one of the best in the league at rushing from the inside. If the Bears don't put the franchise tag on him, his price could skyrocket; and it's worth questioning how much the Bears would want to pay for him.
Since drafting Shea McClellin in the first round of the 2012 draft, it's been widely speculated that General Manager Phil Emery wants his team to switch to a 3-4 defense, if that's true he certainly won't break the bank for Melton.
If Melton leaves, the Bears are left with few certainties on their defense. Stephen Paea and Matt Toeaina are the only defensive tackles under contract. Both are ideally suited to be nose tackles, although Paea could possibly play the three-technique.
It was at one time thought that Julius Peppers wanted to play outside linebacker in a 3-4 defense, but it seems unlikely that he still has the speed and quickness to play that position. Still, I have no doubt about Julius Peppers ability to play end in a 3-4 defense. He may not quite have the strength of Houston's J.J. Watt, but he's still a physical freak who has been a dominant run defender over the years.
If the Bears do make a move to the 3-4, keeping Israel Idonije should be a priority because he seems ideally suited as an end in that scheme.
They also have question marks at linebacker as three of their top four—Brian Urlacher, Nick Roach and Geno Hayes—are unrestricted free agents. A move inside could be best for linebacker, Lance Briggs, and he could be joined by Urlacher or Roach, should they decide to bring one of them back.
The rush linebacker spot opposite McClellin would be a question mark with Corey Wootton likely being trade bait or used as a situational pass rusher on the defensive line. Rush linebackers are relatively easy to find, at least easier than a pass-rushing defensive tackle to replace Melton.
The Bears secondary should be good, regardless of scheme. They'd still almost certainly like to add a third cornerback, but Charles Tillman and Tim Jennings showed they were capable of playing man coverage last season.
While the switch to the 3-4 could be relatively seamless, it doesn't seem practical for the Bears. As the saying goes: You don't fix what isn't broken. While Tucker has connections to 3-4 gurus Saban and Crennel, both of them are from the Bill Belichick tree, and he switched to a 4-3 after winning five Super Bowls as a coordinator or head coach in the 3-4. Belichick still mixes his defense up, showing some 3-4 looks and that could be where the Bears are headed. They showed glimpses of that last season with their Boise Package. Tucker's ability to be flexible is a big bonus for the Bears.
The Bears have a gem in Melton. Pass rushers of his size and athleticism are hard to find and should be kept. He's improved every year in the league and there's no reason to think that improvement won't continue. Melton has the ability to be a cornerstone for the defense for years to come. Keeping him should be their top offseason priority, if it isn't, bigger changes could be in the works.