I have Messi as well and sent an e-mail to ESPN Soccernet. This was the reply from Dale Johnson:
As per the official How to Play game rules:
* The first was an own goal, which there are no assists for. * The second came off the post, which there are no assists for. * The third was flicked on by Burdisso. * The final was an Aguero assist.
The How to Play states: A Key Contribution (assist) is awarded to a player who plays the final successful pass which leads to a goal. Please note that Key Contributions are not awarded to players who are fouled for free-kicks or penalties which lead to goals, for own goals or for goals which result from rebounds off other players or the woodwork.