UFC didnt test for shit till USADA, guys were roided all over the place... Cro Cop is actually 1-0 under USADA, since his only fight under USADA was vs Gonzaga 2 ( Although it was in Poland, im not quite sure who did the testing there ).
Mirko really never got used to the cage though, and young Gonzaga indroduced him to elbows in a brutal fashion right at the start of his UFC career. Reality is, ring favours strikers and cage favours wrestlers, Mirkos stalking style was made and developed in a ring, as we have seen in his K1 career where he beat a solid list of guys, and he transfered that style to Pride perfectly. Octagonal cage and elbows on the ground, its a totally different game....
After loss to Gonzaga, he started really strong vs Kongo, who was juiced to the gills, almost UBEREEM levels of horsemeat, but then Kongo kneed him in the nuts like 6 times in the 2nd round, Mirko continued but couldnt do shit...
His contract ended with that fight, lost of motivation, injuries, inability to adapt his style to the cage, i think that was the 1st time he announced retirement, and we know how many times he went back and gave it another shot. 2nd time in UFC he started ok but then ran into a young stud Dos Santos, he fought well for a while, did sink in some shots, but Dos Santos was motivated, young, big, skilled... Mir Schaub and Nelson fights were pretty sad though, Mirko looked unmotivated, flat footed, even said it himself he was thinking about fishing in between rounds. Took a rest after that, probably took some mexican supplements, healed up banked knees and shoulders and went for another run, winning his next 8 fights and a weak but dangerous K-1 tournament, to end his career. And still might come back to fight Fedor, if Fedor accepts the challenge...
Guy is a legend, a pioneer, first truly schooled heavyweight striker in mma, insane tdd, definetly in my top 5 HWs of all time...
Also remember, back in the day they fought every 2 months, hell Randleman KOed Mirko into oblivion, Mirko had a fight 3 WEEKS aftar that KO... Nowadays they arent allowed to even spar for 5 months... Back in the day you fight 8 times a year, to keep you sharp, they just lining up everyone, cans, pro wrestlers, kickboxers, street fighters, champions, they all want to win, and we all get to discover which style works, some times even twice in one night...