After starring for DC United and Real Salt Lake in the Major League Soccer, Adu, who at the age of 14 in 2004 became the youngest American to sign a professional contract in any team sport when he joined the Black and Reds, moved to Europe, with Portuguese giants Benfica beating a host of other clubs to get the teenager’s signature in the summer of 2007.
Adu’s spell in Portugal did not quite go to plan and he was loaned out to AS Monaco after just one season before spending further temporary spells with the likes of Belenenses, Aris and Rizespor in Turkey.
Adu’s time with Benfica coincided with the arrival of Di Maria from Rosario Central and the Argentine has since gone on to star for the likes of Real Madrid, Manchester United and Paris Saint Germain while the Ghanaian-born is now plying his trade with Swedish third tier side Osterlen FF at the age of 31.
"The biggest mistake I made in my career was leaving Benfica on loan to Monaco," Adu told The Blue Wire Podcast.
"I say it from the heart. It was one of those decisions that, if I could take it again, I wouldn't make it.
"I had three coaches in a year in Benfica. The club was in such a dysfunctional moment that I just wanted to get out of there and go the other way as soon as possible.
"But it turned out to be the worst decision. I joined the club at the same time as Di María. In the first year, I was better than him.
"I played better than him, but I decided to leave for Monaco on loan. And Di María stayed at Benfica. And guess what?
"He had the chance to play with a coach who later came and became a starter. A year or two later he went to Real Madrid. And I ended up being loaned to a secondary team.
"I made the worst possible decision for my career. It is my biggest regret."