Sports games market is big but 2K Sports' share of it can't be that big. NFL games are the best-sellers and they've been shut out of it for 3-4 years.
There are a lot of guys still playing NFL2K5, which was released in 2004, with updated rosters.
There is a big resentment of EA among those people, starting with blaming the demise of the DC on EA's refusal to support it. You have to remember that the 2K sports games were originally published as Sega Sports games.