An Ernie Sims-for-Keith Bulluck swap?

Tom Kowalski of Mlive.com believes there must be more to Detroit's trade of linebacker Ernie Sims: "It doesn't seem conceivable that the team would open yet another hole in the starting defensive lineup without a plan in place to fill it."

SimsSims BulluckBulluckTwitter pal @Schottey has been floating free-agent linebacker Keith Bulluck's name all day as a potential replacement. Bulluck, after all, played under Lions coach Jim Schwartz when both were at Tennessee, and he's available as he recuperates from a torn anterior cruciate ligament in his left knee.

So what gives?

I think you can rest assured the Lions have a plan for the position, even if it means a competition between untested veterans and perhaps a draft choice or two. You can't have a proven veteran at every position. Fewer than five months have passed since Bulluck, 32, suffered the injury. Would he be an upgrade over Sims? It might be hard to know at this point. In general, I'm not in favor of signing 32-year-old linebackers coming off major knee surgery to replace 25-year-old former first-round picks.

Scouts Inc. Jeremy Green included Bulluck among the best five remaining defensive free agents. Here's how Green evaluated Bulluck's situation:

If he is healthy, Bulluck is definitely one of the top players still available in unrestricted free agency. He tore a knee ligament in late December and might not be ready to join a team. When healthy, he is an active linebacker with excellent instincts for the position. He is a sideline-to-sideline player who can make plays all over the field. Though not as active in coverage as he once was, Bulluck still can make plays on balls thrown in front of him. The main reason he is still available has to do with injury.

Bulluck might well be on the Lions' list of possibilities here. But did they trade Sims with the expectation that Bulluck would replace him? I'm thinking the two issues are mutually exclusive. Sims is in Philadelphia now because he didn't play well the past two seasons and he was entering the final year of his contract. This trade didn't open up a hole as much as it, for now, maintained one.