Seattle is blessed with one of the better defensive midfielders in the league with Osvaldo Alonso. He is tenacious, intelligent and a quality passer. He happens to have a powerful foot that doesn't get much lift on the ball and so takes some longer shots.

He has been paired with Brad Evans, Nathan Sturgis, Peter Vagenas, Michael Seamon and some dude not on the team any more. Alvaro Fernandez also has shown up centrally, as has Patrick Ianni. Each of these players add different strengths to the midfield. How they pair, or more, is as much about chemistry as it is about tactical positioning.

When we talk about formations, and the difference between three bands or four, or even five, we are talking most extensively about the midfielders. Those whose role it is to defend, to possess and to attack, but in differing ratios based on their position on the pitch as well as the talents of the individual.

Let's look just at the bands that we call "the midfield." We will ignore the one or two bands that the forwards can claim, and the 1.5 bands that the defense occupies (wingbacks and sweepers occupy similar bands defensive midfielders).

When we see a formation listed as a traditional 4-4-2. The midfield band is considered singular, but really is generally bowed, sidereal calls it the Bucket. The wide players are generally further forward.

The 4-2-3-1 has two bands. With two Defensive Mids (sometimes the switch both can be called Centrals, others they have primary sides of the pitch). The line of three can vary quite a bit though, but usually has one in an Attacking Mid role with the other two wide and expected to be primarily attacking players, rather than Box-to-Box types.

While in some levels of the sport they have speculated that the Box2Box is dead, there are still players who have equal ability and expectation at defense, possession and attack. For the Sounders we see Evans and Vagenas as these types of player.

The Center Attacking Mid is a player with great vision. The number 10. The one whose role is to make the plays, to create the offense, usually half a midfielder and half a forward. Carlos Valderrama was a great MLS CAM. Steve Ralston was as well. Seattle tried Freddie Ljungberg in this role, but having a Withdrawn Forward and CAM puts two guys in the same space and very similar roles. That was part of the problem between the Freddyain. With Seattle running two CDMs lately Montero works as both CAM and WF these days.

There's also a funky little guy called a Deep Lying Playmaker. Who occupies space like a CDM/CM hybrid, but has the vision of a CAM using long balls to fuel the attack. Dax McCarty is the MLS player who most exemplifies this role. The DLP can create the quickest transition from defense to offense as it takes only one pass.

If we think of these Central Midfield roles on the following grid, how do the Sounders current midfielders fit?

Osvaldo Alonso is a great defensive player with some skills at ball possession and short passing. His scoring and passing in crowds is a little wanting. Honestly, he's the ideal CDM. He'd be an OK CM and likely a poor CAM.

Sturgis is the man we see the most often centrally these days. His defense is pretty good. He's an alright possesion guy and outside of set-plays has demonstrated limited skills in attack. He's an OK CDM, an OK CM and a poor CAM.

Do you remember Brad Evans, man of vision and tactical awareness? He is a good CM, a passable CAM and an OK CDM. He occupies space well, sees the shape of both sides to Seattle's advantage and can create scoring opportunities.

El Flaco has intrigued us as a central guy, though we don't see him much. He's got great on-ball skills, and decent vision. His defense is solid, if unspectacular. He'd be a good CAM (though likely not great), a good CM, and likely a poor CDM.

Coach Vagenas is best at the possession game. His defense and attacking skills are not how he contributes. He's a decent CM, and likely best as a CDM.

SeamonSays has some solid dribbling skills and is a decent passer if not under pressure. He fits as a CM, with some leanings to a CAM, but he certainly isn't Alonso insurance.

The point is that Seattle has played with either two CDMs or a CDM and a CM when it is at its best last half of 2010, last 10 of 2009. And while some may say that a central midfielder is a central midfielder let's not confuse the central version of Landon Donovan with Maurice Edu.