Again, he is probably the 4th best center and not even the 6th best Guard in the Big Ten. I believe with another year, he improves his draft stock by 2 rounds minimum.
I have already agreed that the risk of injury is tough, but I just don't believe you see teams take a flyer on an interior OL like they do a QB, WR, DE, DB, LB or even OT. Very few teams are going to use a 1st or 2nd on an Interior OL unless that dude is proven special. Jurgens hasn't yet proven to be special.
The money isn't going to be a whole lot different for him next year than it is this year, unless he becomes an All American or First Team All Big Ten. So if he doesn't think he can make that leap, then maybe it is best for him to leave now. I think he has that potential.