Mane, a summer £34m signing from Southampton, was on fire against the Spanish giants at Wembley on Saturday, making one and scoring his first for the club in a 4-0 friendly romp.
And Lallana claims Mane’s unpredictability could make him Liverpool’s most lethal weapon.
He said: “I knew straight away what he was about. I knew what he was going to bring to the team, regardless of what everyone has seen in pre-season.
“You saw all those different parts against Barcelona but I saw them all in his first couple of sessions. We have seen it from working with him what he can do.
“I was never worried about him settling. He could have had a goal in the friendly against AC Milan but it didn’t matter. I could see what he was going to bring to this team.
“He is different to what we have got. He is unpredictable. He can go down the outside, he can come inside, he has got a goal in his locker like he produced against Barcelona.