Mascherano was doing a three man job for most of the 2nd half.
He constantly had to play RB/RW for Alves along with being a CB. It's not the first time he had to cover someone's ass either, it's the same when Adriano plays as a LB he's always doing a two man job to cover them.
He probably won't do that but I think in games like this when we have problems to create chances (like in 1st half) and he plays 25-30m from opponents goal he should try to shot on goal even more often.