Alan Pogroszewski (St. John Fisher College) has published When is a CPA as Important as Your ERA? A Comprehensive Evaluation and Examination of State Tax Issues on Professional Athletes, 19 Marq. Sports L. Rev. 395 (2009).  Here is part of the Introduction:

This article will begin with a historical look at the states’ ability to tax both their resident and those nonresidents who earn income within their borders by reviewing the Supreme Court’s interpretation whether this is within the state’s constitutional power. This will be followed by an examination on how individual states came to determine the apportionment of income of a nonresident. This section reviews the individual state court decisions that define the tax implications to off season training, spring training the post season, and the allocation of athletes playing and signing bonus for a nonresident athlete. The article then examines the practical application of this tax in whether or not states increase their overall income tax revenue by this practice. Research in this section indicates that they in fact do. The article then concludes with the practical consequences on how these laws affect individual athletes. This Article concludes with the fact that there may be at least one reason why you may want to sign a free agent client with the Tampa Bay Rays rather than with the San Diego Padres.  [Editor's note:  ouch.]

[Click on chart to enlarge.]