It is an intellectually dishonest comparison when one guy's first 24 pitching starts are at age 21 and the other guy's first 24 pitching starts take you up to age 26 (due to the fact that he played overseas for his early-20's). We can apply the same logic to the Willie Mays comparisons, though I would have to research his numbers more than I do Clemens.
He is the league leader in several hitting categories and is far and away the best hitter in baseball this year. However, having him an All Star as a pitcher is little more than a gimmick. He doesn't even have enough IP to qualify as a league leader in pitching.
If you took away all his pitching, he would be the best hitter in baseball and an All Star starter.
If you took away all his hitting, he would have had a nice 4-day vacation this week.