Mirko "Cro Cop" Filipovic has fought pretty much everywhere that Alistair Overeem has - Pride, K-1, Dream, and the UFC. They both have very impressive resumes, and even fought each other once (in a bout that went to a no contest due to some brutal knees to the groin by Overeem). It seems that Cro Cop is not Alistair's biggest fan though, and says he wasn't surprised by Antonio Silva's win over him at UFC 156. He basically went off on Overeem in an interview with Fight Site, saying that Overeem wasn't the same' without the drugs' and that he needed to be put in his place:

"I wasn't surprised by Silva's victory at all and I had believed he would win. I don't want to come off as a smart-ass or say I knew it all along, so I'll explain why I'd believed so. First, Silva is a big tough guy with a huge heart who had demolished Fedor and he needs no better reference than that, and Alistair hugely underestimated him and belittled him with his arrogant statements, so this mobilized Silva in the best possible way. Second, Silva is a natural heavyweight, and Alistair - for the first time since way back in 2007, when he began to gain huge weight - fought without the drugs he had used constantly for years, including testosterone and all the other shit that goes with it."

"Watching the weigh-in, I saw that his muscles mass was nowhere near his usual, he had the weight, but he wasn't nearly as carved out and defined, since he couldn't take anything because he was watched by the Athletic Commission. This also reflects on the psyche of a man who's been using stuff to increase his strength, endurance, pain tolerance and aggressiveness for years, and now there was none of that. Alistair is an excellent fighter, but he still owes that excellence to something that's dirty and unpermitted, and, in the end, very dangerous to health."

"I don't think he was concerned by that, he wanted success at any cost. And the third thing is, Alistair had behaved so arrogantly that someone needed to put him back in his place. His belittling of Silva was repulsive, saying that after beating up Silva he'd go for the belt, and at the weigh-in and entering the arena he acted like he invented the fighting sport, and he's been behaving with so much arrogance lately that I'm glad Silva put him back in his place and taught him a lesson! Congratulations Silva, from the heart!"