In the final third of last season there were few defenders in the world better than the Reds centre-back, according to his manager
Jurgen Klopp believes Joel Matip's influence on his Champions League-winning Liverpool side is underrated, believing him to be one of the best in the world during the final part of last season.
"I think everything about him has been said, what a guy he is, what a player he is, but not a lot of people spoke about the impact Joel Matip had in the last third of the season," Klopp said.
"I don't see a lot of centre-backs in the world who are better in that period, 100 per cent, pretty much without any mistakes.
"Virgil was the constant in that last line [of defence] and it felt always good when you saw him there. He organises a lot of things on the pitch. He's a fantastic player and was a pretty good signing."
The impact of James Milner in the Liverpool dressing room has also become clear and while Klopp feels the 33-year-old still has plenty to offer as a player, he would be willing to offer the former England international an opportunity to cut his teeth as a coach at Anfield.
"There are still a few good years to come [from Milner] and I’m not sure if we already have to think about what he can do after his career," Klopp added.
"But I'm pretty sure for a guy like him there's always a door open at our club, 100 per cent.
"You could see in different moments last season how much it meant to him, four years back [when Milner joined on a free transfer] I don't know what people in Liverpool thought about him, but it was a brilliant idea in that moment because without players like Milly success in football is impossible."
Liverpool open their USA tour with that match against Dortmund on Friday, followed by a contest against Sevilla on Sunday and finish up their American trip against Sporting CP on July 24.