The biggest problem with a salary cap in MLB is not the cap so much as it is the revenue end of things. That will ultimately be the biggest challenge to the cap system in the NFL, too. It works so long as revenues from top to bottom of the league are within some defined band. The NFL's financial structure with respect to TV revenue when teh cap was first implemented had a pretty good revenue distribution. Teams are finding a way, as they always do under any system, to exploit more revenue streams to either enhance their competitiveness or to line the owner's pockets. The NLF is also 'blessed', in a sense, by the very insular nature of the sport: it's basically only played here, and the only 'apprenticeship' you can serve is as part of the US college system. Any sport that is truly international in nature presents a whole bunch of different problems in terms of bringing in talent. The US leagues (MLB and NBA) like to think of themselves as the only 'true' destination for athletes who play these games, and while this is certainly more true for MLB than the NBA, that may change as the games grow in popularity (though much more quickly for hoops than baseball) and the sport becomes more international. Basketball has a bigger challenge as there are more potential lucrative leagues out there given the popularity of the sport in Europe, combined with the phenomenon of an overabundance of talent for comparatively small rosters. Other than Japan, there is no potential for any other competitive league in any viable market any time soon. Other than Japan, the game is really only widely popular in Latin America, and the ability to maintain an economically competitive league there is non-existent at present. Combine that with the fact that rosters are comparatively large for baseball, and that talent (especially in pitchiing) is scarce A cap only works with solid revenue equalisation (or at least mitigation of big revenue variances within the league) in addition to a tightening of the developmental and entry systems. But I think with respect to simply worrying about international players, a cap of some kind could be useful. Maybe even just a secondary cap on spending on transfer fees to non-MLB clubs/non-MLB free agents would help, combined with a rule that states that no foreign player can be signed by an MLB club as a free agent unless that player has built up 'service time' in an approved foreign league, or is signed straight from amateur status.