The Japanese star is set to join the Reds in January after Liverpool activated a £7.25 million release clause in his contract.
Jurgen Klopp made his move for the 24-year-old after being impressed over the two matches between the sides in the Champions League.
German coach Rangnick oversees the technical development of Red Bull’s sports teams within his role as head of sport for the group, and feels it is another astute buy from his fellow countryman.
“You could see he was good on the ball, very technical, good mentality,” Ragnick told Sky Sports . “He is also like many Japanese players, willing to invest in the team’s efforts to win the ball back.
“Of course he had to learn those things tactically, but his willingness and his mentality was already there. He’s not the kind of player to say, ‘OK the other team has got the ball so, please let me know once we have the ball so I then can take part in the game again’.
“Even at the age of 19 you could see he was a good boy.”
Minamino would be the latest player to move to Anfield having been associated with Ragnick.
He will follow in the footsteps of Roberto Firmino, Joel Matip, and former Red Bull stars Naby Keita and Sadio Mane.
“The style [at Salzburg] is very similar to Jurgen’s,” Ragnick added. “It’s proactive, it’s high pressing, counter-pressing. Once we have won the ball we don’t want to waste any time by square passes or back passes.
“We are trying to play forward as quickly as possible, trying to create chances, trying to score as many goals as possible.”
Salzburg’s sporting director Christoph Freund confirmed on Thursday that the club had been in discussions with Liverpool over the sale of Minamino.
Klopp values Minamino at around three times higher than his current asking price, and has beat off competition from Man Utd for his signature.
He could now be in line to make his debut in the FA Cup third round clash with Merseyside rivals Everton on January 5, subject to the deal being completed after a medical.