[Mr. Mulliner]

Obviously there aren't many people, at least in major sports, who have won an MVP in their rookie season. Wes Unseld of the Bullets (now Wizards) is the only guy who comes to mind, but I don't know if he won any later on. Perhaps it's worth checking out.

[Flashlight]

...Obviously there aren't many people, at least in major sports, who have won an MVP in their rookie season...

That's what I was thinking, but read the question again. The athlete won a "championship", not an "award." I'm thinking that "championship" refers to a team world champion (not Western division championship, for example), and not a "statistics" champion, like a "batting championship."

Also, the guy could have had a short carreer of three years and still fulfill the requirements.