Evaluating the defense is immensely more difficult and complicated than the offense. Defensive performance, at least for individual players, is much harder to quantify statistically, especially in today's NFL. For instance, the basic statistics (sacks, tackles, etc.) would seem to tell you that Clay Matthews had perhaps the worst  year of his young career last year. His sack total was way down, and if there's any statistic that tells you something about a pass rusher, it's sacks, right? Well, not necessarily. So much of what goes into a sack is out of an individual player's control that it's impossible to gauge their effectiveness by that number alone. The coverage has to be right, the blocking has to be wrong, the other defenders all have to do their job, and the defender still has to do their job exactly right for a sack to take place.

But as we all know, there are more ways to be effective on defense. It's obviously oversimplifying, but just look at how cornerbacks are used. In zone coverage, a corner can be effective by essentially just standing in the right place. Is there a stat to measure that? Can we look things up and say "oh wow, Tramon Williams had a lot of really good zone coverage this year"? To a certain extent, yes, thanks to some of the advanced statistic sites, but generally speaking it's very hard to compare players based on stats.

With that in mind, I'm going to take a little bit of a different approach to my first half evaluation of the defense than I did with the offense. Instead of looking at each player individually, I'm going to hand out three "awards" for the three major position groups: the defensive line, linebackers, and defensive backs. I'll identify the most Impressive player so far, the most Improved player this year, and the most Important player for the second half of the season.

Defensive Line

Impressive - C.J. Wilson (19 tackles, 2.5 sacks) - Quick, name the Packers' starting defensive ends. Don't worry, I'll give you a second. It's tough, right? According to the Packers.com depth chart, Wilson is currently the starter at right defensive end, although I bet if you asked 10 Packer fans who wears number 98, they wouldn't be able to tell you. But that doesn't mean that Wilson hasn't been having an impressive season.

A third year player out of East Carolina, Wilson is on pace for career highs in tackles and has already set career highs in sacks and games started. Although he's technically slightly undersized for the position, to my eyes he's held up well at defensive end, proving to be fairly stout against the run and relatively effective against the pass too. What's more, he's managed to keep second round draft pick Jerel Worthy off the field, no easy feat considering Worthy was no doubt drafted with a starting position in mind.

Improved - Mike Neal (6 tackles, 2 sacks) - After he earned a four game suspension this offseason (allegedly for using prescription Adderall, but still), I feared for Neal's future with the Packers. A former second round pick, he had flashed great potential during early parts of his rookie season before an injury shelved  him for the rest of the year. Last year, Neal was the presumed starter before hurting his knee in training camp and never regaining his form. This year, though, Neal has managed to stay healthy, and he's slowly earned more playing time as a result. If he can continue to stay healthy, I think he may push for a spot in the starting lineup in the near future.

Important - B.J. Raji (9 tackles, 0 sacks) - Raji's presence is not so much seen as felt. The point man on the defensive line, Raji's health throughout the rest of the season may prove to be the difference in whether or not the Packers make a deep playoff run or another early exit. As the nose tackle, Raji's job is to eat up blocks and free up space for the linebackers to run around and wreak havoc, and there's no doubt in my mind that the running space has been a lot more limited with Raji on the sidelines the last two games.

Linebackers

Impressive - Clay Matthews (31 tackles, 9 sacks) - Who else could it be? Although he's been a little bit less of a force since his six sack barrage in the first two games of the year, the Claymaker has still been a thorn in the side of every offense he's faced. He may be the single most fun player to watch on the Packer defense, if only because he never gives up on a play.

Improved - Erik Walden (26 tackles, 1 sack, 1 INT) - After a one game suspension to start the season, Walden has been a regular in the rotation at linebacker. He only has one sack this year, but he's spending a lot more time in opposing backfields than we've ever seen before. With Nick Perry spending the rest of this season on injured reserve, Walden's ever-expanding role becomes even more important.

Important - A.J. Hawk (66 tackles, 1 sack) - I was tempted to put Clay Matthews here as well, but he's already got one award, so we need to share. And truth be told, Hawk has an enormous role to play throughout the rest of the season. With Desmond Bishop out since the preseason and D.J. Smith joining him on injured reserve earlier this year, Hawk is the only player on the roster with any real experience at inside linebacker. As the injuries continue to mount, Mr. Hawk's responsibilities will likely continue to increase as well, especially if Clay Matthews' hamstring injury keeps him out for any extended time.

Defensive Backs

Impressive - Casey Hayward (32 tackles, 4 INT, 9 passes defensed) - It's hard to know what to expect from rookies, especially rookies playing a difficult position like cornerback. Whatever you thought Casey Hayward would accomplish this year, I can almost guarantee this wasn't it. The former Commodore looks like a seasoned veteran, displaying an astounding acumen for playing the ball in the air. I'm excited for the future of young Mr. Hayward.

Improved - Sam Shields (18 tackles, 1 INT, 3 passes defensed) -  A darling of the 2010 Super Bowl run, Shields struggled through much of last year. Even as late as the last two weeks of the preseason this year, there was some talk that Shields could be without a job when the regular season rolled around. He stepped his game up and was in the mix for the starting job across from Tramon Williams for much of the season so far, until an injury sent him to the sidelines. He's improved this year, but whether or not he's able to return this year and regain his improved form will be an interesting storyline for the second half.

Important - Tramon Williams (43 tackles, 2 INT, 11 passes defensed) - With Charles Woodson still out for a few more weeks at least, Williams is without a doubt the most important remaining member of the secondary. With two games remaining against Calvin "Megatron" Johnson, a date with Victor Cruz, another meeting with Brandon Marshall, and two contests with Minnesota's Percey Harvin on the way, Williams certainly has his work cut out for him. Whether or not he rises to the challenge could go a long way as far as determining the fate of the Packers this year.