Former Schalke assistant coach Sven Hubscher says Kevin-Prince Boateng's self-confidence set him apart from his team-mates during his playing days at the club.
He joined the Bundesliga side from AC Milan in 2013 and went on to feature in 58 games in all competitions and scored seven goals.
The 31-year-old, who is currently at Beşiktaş J.K helped Schalke qualify for the UEFA Champions League in his first season.
And coach Sven Hubscher has offered an insight into the Boateng's enigmatic personality.
"He was enormously confident, but also open, polite and reserved," Hubscher told Goal and SPOX. "He expresses his opinion when he thinks it is necessary, but always keeps his decency.
"Back then, we used it as the cornerstone on which our many young players could find direction in for themselves.
"We talked about him for the first time at a training camp in Doha. When it turned out that there was an opportunity to sign him, [Schalke coach] Jens Keller called him.
"Boateng just said: ‘Coach, put the No.9 shirt aside, we'll rock this thing’.
"He was exactly the experienced player we needed. I still remember his first game against Leverkusen in front of a home crowd.
"He was playing at No.6 at the time. In one situation, Max Meyer did not pass to him, but played a pass out wide.
"Since the situation was near the dugout, it was very easy to hear him (Boateng) shouting: ‘Max, play me over. Max! Max!’ Meyer just replied that Boateng had been covered.
"He replied: ‘I don't give a sh*t, play me over’. We missed having such a player like that before."
On his departure from the club, Hubscher said, "It wasn’t for a personality reason, we simply could not get his susceptibility to injury under control."
"He was no longer as efficient as we were, and he too would have wished for it to be the case because even under Roberto Di Matteo, whom he always addressed as Mister, he was an important personality."
"His self-confidence. He didn't care whether we played against Leverkusen or Bayern Munich.
"He didn't give a sh*t. He simply had this self-image that everyone has to be guided by. This helped our entire team at this point. And, of course, he could also play very well."
Boateng has played for 13 different clubs over the course of a 14-year career in European football.