When he's being marked like that, the only thing he can do is make passes like that one to Iniesta. When you know that nothing will work through the middle than you make sure that you have wingers that can score. Iniesta, despite his brilliance, is just wasted there because he needs 100 chances to put one away, and in a game like this you won't get more than one chance.
You say he played bad? If Iniesta and Sanchez (that was a brilliant pass) score there, we are talking about two Messi assists and how he 'destroyed' AM with his great passes. Football is a funny game sometimes.