UEFA is to investigate Shakhtar Donetsk's decision to play Fred in Tuesday's Champions League clash against Fenerbahce despite reports he has failed a doping test, following a complaint by the Turkish club.

European football's governing body advised Shakhtar to omit the Brazilian for the third qualifying round first-leg tie in Istanbul, which ended scoreless.

Fred is said to have tested positive for banned diuretic hydrochlorothiazide during the Copa America, and is facing the possibility of a lengthy ban if a second sample confirms the breach.

Shakhtar coach Mircea Lucescu defended the Ukrainian club's decision to name Fred in his team, stating that no official document had been presented and that the request was informal.

However, Turkish Super Lig club Fener has launched an official protest to UEFA, whose control, ethics and disciplinary body is to decide on the matter ahead of the second leg on Aug. 5.