No really, not a joke.
It doesn't sound serious, but this whole thing ...
While Jackson injured his back, he also limped off the field favoring his right leg as he leaned on a trainer. He was then helped into a cart, wheeled off the field and to the locker room. He got out of the cart without assistance but walked very slowly indoors.
The play occurred during a no-pads 7-on-7 drill. Jackson pulled in a 12-yard pass in between cornerback Asante Samuel and linebacker Omar Gaither. There didn't appear to be any contact, but Jackson looked as if he had to twist awkwardly to catch the ball. He dropped to the turf, rolled over and stayed down for several seconds before the training staff ran to him.
... sounds kind of not awesome.
Exactly how did DeSean spend his summer, anyway?