Montoya plays more of a defender role but Alves is still far superior and better for this team despite todays mistake.
If you cant see the way Messi and Alves link up and have been linking up these past couple of months fair enough and Alves has not being doing that purely at the expense of defending.
Quite possibly the worst RB performance I have seen this season was Montoya away to Sociedad. It was a joke.
Odd, because I would say Alves today was far and away the worst RB performance I've seen this season. His mistake wasn't the only instance of him being awful today.