Solved! This is from another forum, read it and weep:
" Hi guys
I think I have the answer for you, unfortunately you are not going to like it!!!
I play MLO and recently unlocked an item called '3rd Pocket or something' like that for use in ML Offline and BAL, I assume this is what you are referring to. I believe I unlocked it after a lot of games, I've already played over 300 I think.
I have a BAL save that is only a few weeks old, I'll load it up in a minute and see if I have 3 item slots. (Never even looked at them before so if I don't have any items to actually use I don't know if I'll even be able to see, will get back to you shortly.)
EDIT: Okay just loaded up my BAL save, the 3rd pocket was still locked. However I checked my consumable items and see I have 3 extra pockets. I used one and that now has unlocked the 3rd slot for my BAL player and left me with 2 consumable pockets which I assume I'd use for another save.
Seeing that I have 3 of them and have played just over 300 MLO games my guess is you earn 1 extra pocket for every 100 games you play online. (Possibly has to be MLO who knows.)
All in all pretty ridiculous that you have to play online, especially that many games, to use something for a game mode that is OFFLINE!
What about the people who choose not to play online or don't even have Internet access to play online if they wanted to, pretty silly! Sorry to be the bearer of bad news!.
For the record checking my items I have earned so far.
25 Fruit (Reduces fatigue by a little)
21 Energy Drinks (Reduces fatirue, I assume more than fruit.)
5 Vitamain Supplements (Greatly reduces fatigue)
4 Power Supplements (Full recovery from fatigue)
1 Training Ladder (Experience points for explosive power)
1 Training Shoes (XP for Long Pass Speed)
1 Training Shoes (XP for Kicking Power)
1 Free Kick Trainer (XP for Shot Accuracy, NOT Place Kicking for osme reason)
1 Treadmill (XP for Stamina)
1 Taping (Slightly quickens recovery from injury)
1 Ultrasound MAchine (Greatly quickens recovery from energy)
2 Extra Pockets (Increases the number of pockets)
Can you earn any of the above playing offline modes or have you guys never seen this stuff before? It seems ridiculous that I am earning all this stuff for a game mode I have barely got started on yet! "
