What's up Calvin Johnson?
Yeah, you would definitely need a license to use a player image. There are a lot of issues with this type of venture.
Copyright infringement:
Photographic images are copyrighted by the photographer who took the image. So using an image without license or permission would be infringing on the copyright of the image.
Right of Publicity:
All people, whether they are famous or not, have the exclusive right to profit off their own name and likeness. So if you use any names or likenesses without license or permission, you would be violating their right of publicity.
Trademark infringement:
If any trademarks are identifiable in the image you use, you would be infringing on that trademark. For instance, if you are doing a design of Derek Jeter and the Yankees "NY" logo is visible on his hat or jersey, that would be infringement.
Licenses:
Many athletes have exclusive sponsorship and individual merchandise agreements, as well as being part of the league and players association merchandising agreement. If you are using a player who is part of an existing license to produce merchandise, you would be violating that agreement.
Violation of any of these issue could get you sued. The only legal way to do it is to get specific license or permission from the individual player or league.
Hope this helps.