Association Mode - which sounds like typical offline, single team mode.
MyCareer - which sounds like offline single player career mode.
MyPlayer - which sounds like online single player career mode.
MyTeam - which sounds like online Team career mode aka Crew.
I think its a great idea to separate offline and online career modes, so that they can apply more restrictions to the online mode to reduce cheesing.
or it could be a new mode like mentioned above that allows you to create and operate a team online against other players. That would be cool too.
It's more than likely this. The achievement list mentions purchasing 'boosters' which I'm guessing are like the card packs you can buy in FIFA's ultimate team mode. Plus, I remember reading someone say that Ronnie told them they had a mode better than My Player for this years game. I'm guessing this is what he was referring to.
Me personally? I'm not that fussed by it. I much prefer running an association to having a fantasy team. I guess it could be entertaining if it's implemented well, though.