Here's what our own Dallas Winston had to say in his live blog of the fight about the critical first round:
R1: Cain comes out pressuring with a 1-2 and then ducks under for a body lock takedown. JDS reverses it, like a boss, and almost takes Cain down. Cain is a little predictable on his next two attempts: he's just unsuccessful on the first but almost walks into a jackhammer on the second. JDS plunges a deep jab and sits down on a few hooks to back Cain off. Cain slings out a series of jabs that find the mark but he fails badly on the single.
JDS cracks him with the same right hand that put him away the first time, but Cain takes it in stride. Cain crowds him up on the fence but JDS sneaks out when he releases his grip to dirty box. Cain blisters a right hand through JDS' guard that drops him on his can. History is made. Cain is in top form and swarming JDS in classic fashion with positional advances and rapid-fire punches.