I think that Mark Coleman presents a bad matchup for Mauricio "Shogun" Rua going into their UFC 93 fight in Ireland.
Coleman is a wrestler dating back to his seventh place finish in the 1992 Barcelona Olympics. He was the guy that brought wrestling into the UFC as a formidable style, using it to win both the UFC 10 and UFC 11 tournaments.
Six of his fights have gone past the first round. Of those fights, half were victories and half were defeats. When he loses, he usually loses badly, but the guys who he has lost to were pretty impressive names at the time of those losses (Fedor twice, Cro Cop, Nogeira, Takada, Rizzo, Williams, and Smith all one time).
Wrestlers traditionally give Brazilian Jiu-Jitsu fighters a lot of problems, unless the Brazilian Jiu-Jitsu fighter puts the wrestler on his back. I don't honestly see Rua getting up the leverage or the advantage necessary to put Coleman in that position.
Rua had issues with Forrest Griffin's size the last time he fought, ended up getting tired and giving his back up. Griffin has historically had problems putting people away. Coleman doesn't have that issue, and I think he will spring on any weakness Rua has.
Both guys are coming off of injuries that have prevented them from fighting their last scheduled fight. Coleman was scheduled to fight Lesnar at UFC 87, but had to back out due to a knee issue, and Rua has had running problems with an Achillies injury which caused him to miss UFC 85 against Rashad Evans.
I think this bout was thrown together to add some known names to the pay per view taking place away from the United States, and Rua has the most to lose and will lose the most from being pitted against Coleman again.
All that being said, it is Mixed Martial Arts and anything can happen.