Ghana football (soccer) midfielder Michael Essien has become the English football club Chelsea's most expensive signing, after passing his medical exam Friday.

The 22-year-old signed a five-year contract with Chelsea after the French club Lyon sold his rights for $47 million. Essien has secured a work permit, but it is not known if coach José Mourinho will put him into Sunday's match against Arsenal.

The French first division player of the year in 2004, Essien is expected to compete with Claude Makelele for a place alongside Frank Lampard in the central midfield.

Essien's signing is part of Chelsea's $100 million campaign for this season. The English Premiership title winners also have signed French-born defensive midfielder Lassana Diarra, Englishman Shaun Wright Phillips and Spanish defender Asier del Horno.

Some information for this report provided by AP and Reuters.