Thursday 26 November 2015 14:40, UK
The suspension for Dinamo Zagreb's Arijan Ademi was because of a positive test for the anabolic steroid stanozolol.
The 24-year-old central midfielder was given a four-year suspension for failing a drug test after his team's 2-1 home win over Arsenal in the Champions League in September.
UEFA did not identify the substance in his urine sample when the ban was announced on November 20, but on Thursday Europe's governing body revealed that it was stanozolol - best known as the substance Canadian sprinter Ben Johnson was caught using at the 1988 Olympics.
Following the defeat against Dinamo, Arsenal coach Arsene Wenger criticised UEFA's anti-doping program and the rule which allowed the victory to stand because only one player tested positive.
UEFA defended its anti-doping program on its website on Thursday and stated Ademi's four-year ban followed World Anti-Doping Agency guidance for "a first serious doping offence".
The Macedonia international, who has made three international appearances, has said he will appeal.
After hearing of his ban, Ademi said: "I am at a loss of words to describe how terrible I feel. I am not guilty, I know that I did nothing wrong but still received a drastic punishment."
Dinamo have previously said they would support the player. Dinamo coach Zoran Mamic revealed recently the club was shocked and intended to appeal the decision to the Court of Sports Arbitration (CAS).
