Brazil’s Fred failed a drug test during the 2015 Copa America earlier this summer, testing positive for the banned substance hydrochlorothiazide.

The substance is a diuretic that can be used as a masking agent to hide other possible performance enhancing drugs.

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This new information could explain why after featuring for Brazil in their first two matches of the Copa America, Fred was dropped for the final two matches of the tournament.

The midfielder denied any wrongdoing, and the Brazilian federation has said they are behind the player and will offer him any assistance needed to prove his innocence.

However, this could have further complications outside of Brazil, as Fred featured for his club Shakhtar Donetsk against Fenerbahce earlier this week in a Champions League qualifier.

Shakhtar manager Mircea Lucescu said UEFA had advised him not to play the Brazilian midfielder, but he still chose to as it was not an official request.

Before the game, UEFA advised us not to include him but we had not received any official documents and this was just a verbal recommendation.

There is no specific statement on this matter for now and we are still waiting for the results of the B sample.

I have talked to the team and the player personally. When the official decision arrives, of course, we will stick to it.

It is very hard to say what really happened. I guess the Brazil team doctor should be responsible for things like that. I do not think a guy who can run 13 kilometers per game needs pills but I will avoid commenting on the issue further until the results of the second test are known.

However, it would be very sad if such a young player is suspended for some time.”

After the match, which ended in a 0-0 draw, Fenerbahce submitted an official protest to UEFA. A ruling will be issued on August 3, as Shakhtar could be punished for using an ineligible player.

Last season, Polish side Legia Warsaw were thrown out of the Champions League after fielding an ineligible player against Celtic in the qualifying rounds.