The Spencer Haywood case (in 1970) was tied to the notion of sitting out affecting his future earnings. He won, and the floodgates were opened in the NBA.
In this case, Clarett is trying to use the same defense. The difference is that Clarett has been suspended a year by Ohio State for lying to NCAA investigators and for violating rules regarding compensation.
A judge would have to take that into consideration before rendering a verdict. (The judge in the case, ironically enough, is the son of legendary Ohio State coach Woody Hayes)
NFL Player's Union head Gene Upshaw said (in an ESPN article), "We support [the NFL's] position. ... I don't think he should be playing in the NFL yet. He should stay in school. This will be here for him.
"I'm concerned about [him] physically being prepared to play. I'd have loved to have played against a guy who's 18. I'd have whipped him."
He's impatient and greedy. And it's gonna cost him in the long run.