This is one of the biggest questions this Kansas football team will have to answer. It seems to me that since they have nine returning starters everyone (not you, Tully) is just assuming that the defense will be the stalwart they were a year ago. Count me as one that is not so convinced.
For one thing, the competition gets tougher. Secondly, they lost their two best players. I think Kendrick Harper is a fine player, but he is not Aqib Talib. Aside from Talib's fairly impressive stats, you can't discount the value he provided simply by being on the field. True, Talib gambled a little too much to be a true shut-down corner, but he was good enough at it that opposing quarterbacks avoided him when possible.
As with Aqib, it's tough to quantify McClinton's value. But as much as I like Blakesly, Greene and Johnson, Jr. none of them get off the ball like James did. He was never the biggest guy on the line, but he required a double team on nearly every snap because he was way too fast for single coverage. And even then, he was often able to split the blocks and get into the backfield (see: OSU when he nearly took the handoff). I have high hopes for his replacements, but this is a luxury the team will no longer have.
As we all know, the d-line is more about occupying blockers and freeing up their linebackers than making all of the tackles on their own. However, if you can't get a pass rush with four then you can't create much of a pass rush. In any version of the spread (since it seems like everyone is running one) the last thing you want to have to depend on is blitzing your linebackers, because once you do that you leave open some real wide holes in your coverage. With the pass-happy schedule KU has this year, this simply cannot happen unless they plan on scoring 45 points per game.
Here's a quick look at some of last year's stats...
Worried yet? Obviously the most glaring issue is the lack of sacks. But if you look at it as a whole, you can tell that it's really an issue of just getting into the backfield. It's completely inexcusable for your starting D-ends to have a combined 4 QB hurries. McClinton had five by himself.
And that's the kicker. Because you can see that in MUCH less playing time (and to be fair, sometimes against lesser competition) Laptad, Wheeler and Onyegbule were much better at getting back there. But the only one of them that really showed much ability to rush the passer, while also maintaining his assignment was Laptad. This is obviously not a trade-off the staff is willing to make, and understandably so. But with the spike in competition this year, I firmly believe that not only will they have to replace McClinton's production (as well as Haselhorst's), but also improve upon those numbers. I don't think the sack number has to improve dramatically, but without a doubt the pressure does. Unfortunately, I'm not utterly convinced that it will.
I love the depth at safety. I think the corners will be just fine. And the linebacking corps is probably the best in the league. But none of those units can make up for a poor defensive line. As I mentioned earlier, in a league like the Big XII, the last thing a defensive coordinator wants to do is depend on blitzing his linebackers. But if you don't get pressure with four that's exactly what you have to do. Here's to hoping they prove me wrong.