You gotta remember he was locked in the WEC together with Brian Stann, Carlos Condit, Donald Cerrone and Jamie Varner who were all apparently underrated before coming to the UFC. You could make the same statements about them.
His wrestling background which he uses alot and his camp helped him alot in achieving victories in the UFC. The Marquardt fight was a surprise though I also predicted him losing by submission.
Actually, no you can't.
All those guys were pretty much winning their fights, and were semi top fighters before coming to the UFC. Hell, Carlos Condit and Jamie Varner were champions for a good little while. You have to look at records before going onto the UFC...
Carlos Condit (former WEC champion): 23 - 4
Donald Cerrone (Former WEC champion): 13 - 3
Jamie Varner: 19 - 6
Brian Stann: 6 - 1
Cheal Sonnen, at the end of his first UFC stint, was 15 - 8. That's just above a journeyman record. He's been on in 12 - 3 streak since then. He is a change fighter since that point.