Jason "Mayhem" Miller is a UFC, WEC, DREAM, Superbrawl, and Extreme Challenge veteran. So in other words, Miller has been in the game for a long time. Miller recently competed in the DREAM promotion fighting in their GP tournaments. He lost to submission ace Jacare via decision then got a win before re-matching Jacare again, only for the fight to end in a No Contest. Both fighters have vowed to fight again and have traded verbal jabs on the internet. Miller holds an overall record of 22-6-1 NC with 13 wins coming via submission and 4 via KO/TKO. He's very savvy during his fights and incredibly difficult to finish. However, he should enjoy an advantage in this fight while it's on the feet. But, if this fight goes to the ground he will be comfortable there as well.
Jake Shields has been on quite a run as of late, in fact he hasn't lost in almost 5 years. Shields is a veteran of EliteXC, Shooto, and Rumble On The Rock promotions. He holds an overall record of 23-4-1 with 10 wins via submission and 3 via KO/TKO. Shield's strongest asset is his jiu jitsu in which he is a blackbelt under Cesar Gracie.
Shields is the favorite going into this fight but I like Miller's chances to pull off the upset. Shields has incredible jiu jitsu, but Miller has been in there with the likes of Jacare(who could arguably be better than Shields in pure BJJ). So if/when this fight goes to the ground, he will not be a fish out of water so to speak. As I mentioned before, Miller will enjoy the advantage while this fight stays on the feet. These fighters have trained together at different points, so both should be fairly familiar with one another's game. It's doubtful that Shields will be able to submit Miller, but he may be able to control him on the ground. Miller could possibly outpoint Shields on the feet, but I expect Shields to get this fight to the ground at some point, in which he'll probably win via decision.