The "Will" will be Barnett
The "Mike" will be Shepard
The "sam" will be Merriman
Based on the team we currently have this is my prediction
The sam plays at the line when there is a TE on his side. Typically the largest of the group, he has to take on the TE. Why Merriman fits? (*assuming he is healthy) he can hold the line of scrimmage against any TE, playing next to Mario Williams, teams will keep their TE in for blocking duties. In the event that they pass and the TE releases you'll be asking a RT to block Williams or Merriman until he gets help. George Wilson then picks up the TE in coverage. It Kind of looks like a 3-4 with a NG head up on the Center, the 3 playing the gap between the LG and LT (which is called the 3) and the RE outside of the LT. The LE goes pretty close to Heads up over the RT and the Mike plays almost over the RG. The Key to this defense is Will, he has to be able to fly around and make tackles. Barnett is clearly our best LB and makes the most sense. When there isn't a TE on the strong side, Merriman could get lost, I am hoping that his read and react skills are better than many here think.
In the draft, Lavonte David from Neb fits the Will nearly perfectly. Dont'a Hightower has the size to play the Sam and the athletic ability to play the Mike.
Currently I see the following happening.
on run downs (or more than 2 WR are in the game) Merriman plays Sam and Kelsey plays RE. On passing downs they can shuffle Merriman in to RE along with Moats and maybe Batten if he makes the team.