Brian Cushing is taking the death of his former USC teammate, Joe McKnight, very hard ... so says Brian's friend Zac Diles.
Zac -- who played on the Houston Texas with Cushing -- says he spoke with the linebacker hours after the news broke about McKnight ... and he's "very, very distraught."
Cushing has posted the following statement about McKnight:
"Joe I'll never forget the time we had together at SC. It was unbelievable to see you grow and work your ass off from a freshman until the day you were drafted.