In FIFA 12 you could select whether it is possible to select both sides in a match when setting up a new career. We used this with two players in front of one box to level a Pro. Since it's now possible to get the Pro even higher because the difficulty achievements have been removed, this seems to make a lot more sense. But the option seems to have gone. I cannot switch to play the opponent. How can I do that?
There is definitely an option to select "Allow AI Control" (or something to that effect) when you set up a new career. I started a new Manager Career the other day and the option was definitely there for me. I haven't confirmed yet if the same option is available in "Player Career". It would be logically if this wasn't available because if you are meant to be a particular player, then you cannot swap and play for the opposition team.
Another thing worth mentioning. In Fifa 13, you can no longer use your career pro in other game modes. They seem to have restricted him to the mode he is created in. So whatever improvements you unlock can no longer be taken into the on-line world, you have to create a separate player for that.