Benfica won the race to bring Adu to Europe when they forked out £1 million to sign the teenager in July 2007, but he struggled for regular playing time during his first season in Portugal.
The ex-United States international was sent out on loan to Monaco the following year after only managing four goals in 17 appearances for the Primeira Liga giants, which marked the beginning of a downward spiral.
Adu also took in loan spells at Belenenses, Aris and Caykur Rizespor before Benfica cut their losses on the attacker and accepted an offer from Philadelphia Union in 2011.
The 31-year-old has since played for clubs in Brazil, Serbia and Finland, with his latest venture coming in Sweden with Division One outfit Osterlen FF.
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