Originally scheduled for light heavyweight, O'Brien failed to make weight and enters this fight with an automatic yellow card and a 10 percent purse deduction. Mousasi is coming off a Strikeforce title loss to King Mo last April.
The live blog is below.
Round 1: O'Brien immediately shoots and Mousasi sprawls. O'Brien grabs one leg and continues to work for the finish. Mousasi grabs the guillotine, and that's all for O'Brien.
Official time is 31 seconds.
Mousasi wins by submission