I think that you Shields Vs Jacare would be a great fight. Shields gets a lot of hate, but he has great JJ. Is he on the level of Jacare? Maybe not
Definitely not. Palhares isn't on Jacare's level either. Maia, Jacare, Roger and Werdum are the best, then Palhares and Magalhaes. Shields couldn't hang with any of them.
Here is Jacare tapping out Marcelo Garcia in 2 minutes in nogi, Shields would be done for way too quickly.