That could be a possibility. The tumor caused Choi's body to produce absord amounts of Growth Hormone. When the tumor was removed, maybe his body went to normal levels of Growth Hormone, which decreased his performance. Intresting theory.
That was...lame. As a Cro Cop fan, I was eagerly awaiting this one. I didn't see how he could beat someone Choi's size, especially since he doesn't have a ground game. Well, he found a way to win. Let the mummified zombie chase you around for 5 minutes, then kick it in the knee.
I was also wondering what Cro Cop could have set up if he'd taken some side kick lessons from the man in your avatar.
The side kick is a useful tool. More fighters need to use it! It's like a jab and a cross rolled into one.