Briggs never was a good fighter. Big, muscle bound with limited endurance YES. Just missing one critical area.....the ability to fight.
Shannon is slow as molasses, any top 50 heavyweight should be able to see every punch he throws from a mile away. His reflexes are also completely shot. Shannon is looking for one last big pay day, I don't think he's going to get it.
The best guy he's fought in recent years took him the distance and that was Zumbano Love a guy AJ stopped in 2. Reality is he would struggle with anyone inside the top 30, he doesn't beat anyone inside the top 20 and gets badly hurt by anyone in the top 10. Briggs is beyond shot, the fact he's still in good shape and been promoting himself so well is the only reason he's even still mentioned. At this stage Briggs is a better salesman than he is a fighter.