German side Schalke have complained to UEFA over the eligibility of striker Didier Drogba to play for Galatasaray in Wednesday's Champions League last-16 tie.
Schalke, who came away from Istanbul with a 1-1 draw in their first leg clash, believe that the transfer of the former Chelsea striker from Shanghai Shenhua was completed after the registration deadline.
"Reports in the media aroused suspicion that Drogba's application was only submitted after the deadline had expired for registering players for the Champions League," Schalke's head of finance Peter Peters told the club website.
"UEFA specifically point out before every match that clubs are responsible for the eligibility of the players they field.
"They don't usually conduct in-depth investigations themselves as they rely on reports from the clubs and national associations. They only get involved -- as in our case -- if a club lodges a complaint."