If you aren't familiar with Pro Football Focus, you probably should be. The site, especially their premium stats, are a football nerd's dream. I often get lost in their numbers for entire afternoons, mostly looking at how well or poorly Chargers players have performed in the last few years.

Today, however, I'd like to find out how good some the guys the Chargers signed as free agents performed according to PFF's grades. Here's a little rundown on why/how PFF grades, since I know it'll be asked. For the ratings below, assume that a grade of 0 would be average.

Despite turning 30 years old during the Baltimore Raven's training camp last year, Johnson had a heck of a season.

Overall: 19.2

Run Defense: 22.3

Pass Rush: -6.6

Pass Coverage: 1.0

Penalty: 2.0

This isn't far from what we expected. Johnson is incredibly good against the run, but didn't look so hot as a pass rusher in 2011. Johnson was listed as a 4-3 OLB most of the time, playing a hybrid position much like Von Miller did for the Broncos, and finished the season as the 5th highest rated 4-3 OLB.

McClain was awful last year. We all know that. We also all know that he was an awful fit for a Chiefs offense that wanted to spread out and throw the ball as soon as Jamaal Charles went down for the season. Let's take a look at how bad it was.

Overall: -2.9

Rushing: -0.4

Receiving: 2.6

Pass Block: 2.7

Run Block: -7.3

Penalty: -0.5

Just so we're clear, the higher the penalty rating the better the player is at avoiding penalties called on them.

Anyway, McClain was awful at everything last year except keeping his QB clean and catching the ball. Might be a sign that he could handle 3rd Down Running Back duties in obvious passing situations. He was the 20th highest rated Fullback last season.

Overall: 2.4

Receiving: 2.5

Run Block: -2.9

Penalty: 1.6

Meachem was the 26th best rated WR in 2011, one slot higher than Vincent Jackson.

The other new guys, such as Dante Roasario and Eddie Royal, aren't expected to be starters. That's my justification for not posting their numbers, which were actually quite bad. Anyway, there are more rankings than just the ones above and they go back years. If you're into NFL stats, I high recommend you try out Pro Football Focus.