Kellen Winslow Jr. has pled guilty to raping an unconscious 17-year-old girl back during a 2003 incident and now faces up to 18 years in prison.
The ex-NFL star cut a plea deal with prosecutors in his serial rape case involving 5 different accusers -- several of them older transients.
Back in June, Winslow was convicted on 4 criminal charges ... but the jury was deadlocked on 8 remaining charges.
Winslow was due back in a San Diego court Monday for a retrial on the 8 remaining counts but cut a plea deal minutes ago in which he pled guilty to 2 counts -- sexual battery and rape of unconscious person.