If you change "hard" to "pretty much impossible" that's right.
If you couldn't see the face or number on the jersey, but they have a very recognizable one of a kind mask or marker (like at a championship game or something) you'd need a release.
This is all assuming that it's not an organized event that you have a contract to shoot. In that case, your agreement with the event host should cover it all.
Originally Posted by RepomanGene
****ing Ninja my ***...that **** is Black