Watching the videos from the Illinois game, and then going back to the Michigan State game, have confirmed something for me: Denard's mechanics have broken down a bit over the course of the season. This is, in a way, good news. It is good news because it can be accounted for in the play-calling, and because it is fixable.
Denard throws with quite the rotating motion of his upper body. This is not unusual, and is more common with QBs with more of a sidearm delivery. Because of this technque, however, Denard often releases the ball with his chest rotated past the point where it is directly at his target. This can lead to inaccuracy.
To see where this is a problem, watch the Michigan State interceptions. Both were on patterns where the receivers crossed from Denard's right toward the middle of the field. He rushes, and doesn't quite rotate his body enough, leaving the ball behind the receiver.
It is important to note that QBs rarely have their chests perfectly pointed at their target. The target changes slightly even in the moment between when a QB begins his throwing motion, and when the QB releases the pass. So, QBs make small, usually unconscious adjustments with their arm and shoulder - their feet, hips, and chest are already set. THis is not a big deal when a QB is well-squared to his target, but when his technique involves an overrotation of his chest, it makes it more difficult for a right-handed QB to adjust his pass further left. On the other hand, adjusting further right on a throw is easy.
To see this, watch the last two TDs Denard through to Roundtree. Both were routes moving from Denard's left to right - the better route for him. On the shorter, Denard was able to adjust the throw a bit behind the receiver - but still catchable - to avoid a safety. On the longer, he threw one of the prettiest touch passes of his career. I submit that these throws - and any other crossing routes, posts, or slants coming from his left to right - are well-suited to his technique and likely to be accurate.
This is a very common technique problems with a young QB. The fact that he had better technique at the beginning of the year means that he was well-coached in the offseason, but that it hasn't become permanent yet. These technique issues take quite awhile to perfect. But they'll be even better next year, and the year after...
This year, this suggests the play-calling can be done in a way to maximize Denard's effectiveness. Throw posts, slants, and crossing routes to receivers to the left. To the right, throw outs, curls, gos - anything vertical or to the outside. Those are going to be the money plays for the next three games.