Carragher said: “If he continues in the vein he has started I don’t think Alvaro will be just a squad player for too long.
“I’ve played at left-back for the club too, and know that, once you get your head around it, it can be okay.
“But to start out there, and against Messi as well, I think there probably aren’t many Liverpool players, if any, who have had a harder debut on paper.
“To come through that and play as well as he did, it was an outstanding debut. Alvaro made it look easy and that is full credit to him.
“We saw that night what the players have noticed about him in training.
“He looked very sharp and aggressive. He is a very lean player, without too much weight on him, which helps with his mobility.
“He is very quick too, and is a player who can come in and play anywhere across the defence. If you have players who can play in a couple of positions it saves the club a bit of money, too!”
