Talented midfielder who played for Chelsea from 2005 to 2014 then joined AC Milan; became part of Ghana's national team in 2002.
After playing on his local side and the French club Lyon, he signed with Chelsea for £24.4 million, then a record amount for an African footballer, and a record for the club.
He was named Chelsea's Player of the Year in 2006-07 and helped the team win two Premier League titles and four FA Cups during his time with the club.
He was born in Accra, Ghana.
In late 2012, he went on loan to Real Madrid and played under coach Jose Mourinho.