Tbh ... If the game made sense, they would have two sets of arrows.

1. In possession
2. Other team has possession

Unfortunately, we don't have that and I'm not sure if anyone can say 100% for certain what they do (I maybe wrong). Especially as offsides aren't really in the game and there are no individual stats. I guess you could just put forward/backward arrows on everyone and see if you become more attacking/defensive.