Pochettino coached Coutinho while in charge of Espanyol.
"Philippe is a Brazilian player and, as it happens with most Brazilians, he has a special magic in his feet," the Southampton manager told reporters.
"Aside from the magic that he has, he also has an amazing work rate and that makes us doubt whether he fits the mould of a typical Brazilian player or a European one because his work ethic is outstanding.
"What is important about him is he is a good lad, a good kid - a great, humble person.
"I do think Coutinho has that same quality that Ronaldinho and Messi have, but he has much to prove yet.
"What is really clear to me is that Coutinho is a really responsible player - really dedicated and responsible to his own players."