Are you talking about this season, or the future? Assuming the former, the guy is fine as a backup, assuming he doesn't have to play many minutes. Yeah, you'd like his def to be higher, but assuming his IQ is in the normal range for a RS soph, his B+ IQ and 46 def is going to be better than a freshman coming in with a C-/D+ IQ and 60 def.
I certainly wouldn't be thrilled about him, but he's serviceable as a backup.
Now if you're talking about building an NC team three seasons from now, you may be able to find someone better. As I'm sure you're aware, the tradeoff for no offense should be great defense, which means better speed and def. But again, depending on class makeup, he may be a better backup option than an incoming freshman over the next season or two.
Just my .02