Coutinho is expected to complete a loan switch from Barcelona to Bayern this week.
Grujic, who is currently on loan at Hertha Berlin, played alongside Coutinho at Anfield and believes the Brazilian will thrive in Bundesliga.
"He is a special and exciting player, he does crazy things. He got incredible tricks and skills in his locker.
"I enjoyed every training session with him in Liverpool. He will be by far the best footballer in Germany."