In just one year, the Ghanian has gone from a bad-tempered teen to a vital cog in the AC Milan midfield machine.
The wiser ways of AC Milan's Kevin-Prince Boateng
A year ago this week, Kevin-Prince Boateng struck the second goal for Portsmouth in an FA Cup semi-final at Wembley Stadium. It ensured his club would complete an unusual double, competing in a final of football's most celebrated domestic knockout competition the same season they were relegated from the English Premier League.
Boateng, with his goal against Tottenham Hotspur, had played his part in the club's history; his own career was also about to whirr off in unexpected directions.
Had you asked Boateng 12 months ago if he thought his next ten competitive matches would involve him playing at venues such as Soccer City, Johannesburg, and San Siro, Milan, he would have looked at you askance.
Had you said he would be front-page news in Germany for several days in May and June, or that he would be in the peculiar position of playing against his brother in a World Cup finals match, he would probably have shrugged and said he doubted the first possibility and viewed the second as remote.
In April 2010, Kevin-Prince Boateng was a former Germany Under 21 international looking for a new contract at somewhere other than a Portsmouth soon-to-be of the Championship, and waiting for long and tangled red tape to be unravelled that would make eligible to represent Ghana, where his father was born and grew up.
Prince Boateng, Kevin-Prince's father, moved to Germany in the early 1980s. There he met Catherine, whose family tree stretches out to include Helmut Rahn, scorer of the winning goal for West Germany in the 1954 World Cup final. They were not a couple for long after the birth of their two sons — Kevin-Prince the younger of the two — and Prince Boateng senior would go on to father a younger half-brother, Jerome, in what would become quite a footballing family.
Kevin-Prince grew up in the Wedding district of Berlin, which he would later describe as fertile territory for "dealers and gangsters". He chose to try to be a footballer, and his talent earned encouragement from coaches and scouts. He was strong and technically dexterous, would be drafted young into the Hertha Berlin first team and accelerated through the German national age-group squads.
His potential was feted, but by his late teens, some off-the-field incidents began to concern his coaches. He was dropped from the German U21 team after misbehaving at a tournament. He developed a reputation for ostentatious extravagance and public displays of bad temper.
Boateng moved to England at 20, Tottenham Hotspur signing him from Hertha Berlin for €6 million (Dh31.8m). He never established himself in a period of frequent managerial change and would return to Germany 18 months later on a six-month loan at Borussia Dortmund. Spurs sold him to Portsmouth in the summer of 2009.
His prospects as a German international seemed to have faded, though Jerome, his younger brother, was being called up by the senior team. So Boateng began to explore the possibility of representing Ghana, who had been in contact with him ahead of the 2006 World Cup.
But the process, under which Fifa had to decide on his eligibility, would be long, and time appeared to be running out when his clearance to represent The Black Stars had still not arrived at the beginning of May 2010.
Portsmouth by then had been relegated, and took on Chelsea in the FA Cup final with bittersweet feelings. Boateng missed a penalty in the defeat and he also hurt Michael Ballack, the Chelsea midfielder and Germany captain, with a late tackle. It ruled Ballack out of the World Cup.
Cue outrage across the pages of Bild-Zeitung and less measured media in Germany, who called Boateng - the German-turned-Ghanaian - a traitor, and hinted that the fact Ghana were in the same World Cup group as Germany would make that match particularly hard for the older Boateng, especially as the younger Jerome might be playing on the other team.
The friction had indeed become fraternal by then, but Kevin-Prince Boateng could hardly regret his decision to team up with Ghana. He had a fine World Cup, and scored an eye-catching goal to eliminate the United States in the last-16 stage and, but for a cynical handball on the goal-line by the Uruguayan Luis Suarez in the last minute of extra time, Ghana would have reached the last four of the tournament, just as Germany did.
Happily, Kevin-Prince is now talking to brother Jerome, now a Manchester City player, again, "quite often," he said recently.
He admits that he has experienced a dramatic change of fortunes in the past year.
"The World Cup obviously helped me to get the move to AC Milan," he says of his final destination after a complicated summer of transfers. From Portsmouth he moved to Serie A's Genoa, who still co-own his registration. No sooner had he settled in at Milan in August, that "I was told [Zlatan] Ibrahimovic and Robinho were coming".
Had he felt threatened? "I didn't see that as competition for my place, because my role is bit deeper, and it's been great to have these guys up front." Indeed, Boateng's deployment behind a front pair has been among the striking successes of Milan head coach Massimiliano Allegri's debut season.
Should Milan clinch their first scudetto in seven years, Boateng will have played a key part, despite some periods out injured. Milan will want to keep him, too, though Genoa now know very well they made a good investment in banking on a maturer, wiser Boateng.