Let's compare two pitchers. In the not-so-cryptic tradition of analytical baseball blog posts, we'll call the two pitchers "Pitcher A" and "Pitcher B":
As is quite obvious, in every way other than K/9, Pitcher B is performing better than Pitcher A. A is allowing over a run per game more than B (1.33 more when you count unearned runs), is putting more runners on base per inning, and is allowing more home runs. Not only is A's own record worse than B's, but A's team performs much worse with A on the mound than B's team does with B on the mound. With A on the mound, A's team performs like the 1965 Mets. With B on the mound, B's team is the 2001 Mariners.
And the stats here are not the results of some fluky BABIP. A has actually benefited from a BABIP below league average (.287 so far in the NL; .295 in the AL), while B is slightly above the NL average but right at the AL average. The differences aren't that big that we can say either's numbers unfairly represent what's really happening so far.
What about value? Maybe A is a low-priced rookie and B is a high-priced star, and that explains the difference? Actually, it's almost the exact opposite. A's salary for 2013 is $64.5 million, while B is being paid "just" $7.5 million this year.
And there's the rub. A is not one pitcher (no one makes that much money in MLB . . . yet), but rather three. In fact, A is the 2013 composite of three pitchers generally regarded as not just stars, but rather aces -- Cole Hamels, Cliff Lee, and Roy Halladay. B is also not just one pitcher but rather three pitchers generally not regarded as stars, far from it -- Kyle Kendrick, John Lannan, and Jonathan Pettibone.
Of course, there's no reason that this performance gap should continue looking like this for the rest of 2013. Hamels and Lee should shine, even if Halladay continues to puzzle. Kendrick might be improved, but it's hard to believe he's this good. Lannan is a filler, and Pettione is a rookie. By the end of the season no one would be surprised if this chart were completely reversed.
But, this story has to be one of the biggest surprises for the Phillies so far this year -- that the three others are far outpacing the three aces.