Barnsley defender Bambo Diaby has reportedly failed a drugs test and missed last Saturday's 1-0 defeat to the Robins as a result.
The 22-year-old is reported by the Mirror to have pleaded his innocence to his teammates and he insists that he will clear his name, having not been involved in the Tykes' loss at Ashton Gate.
The tabloid claims that a decision to not play Diaby against the Robins was taken internally.
It is understood that Barnsley boss Gerhard Struber called a team meeting last week to tell the players about the situation and he explained at the time that Diaby would not play against Bristol City.
Diaby is believed to have been tested after Barnsley’s defeat at Blackburn on November 23 and has been playing since while the process goes on.
However, no formal announcements have yet been made by either the club, the FA or the player.
Manager Struber said on Monday that Diaby was struggling with a knee problem as he missed Saturday's defeat to City and Tuesday's 3-0 loss against Preston North End.
"The situation is not clear, the process is running," said Struber.
"The information comes next week and we can tell more about Bambo then."
Positive drug tests can result in a four-year ban as the maximum punishment.
Cases take a long time to be processed and they remain rare in football. Diaby has played 21 games for the Tykes this Championship season, with his last appearance coming in a 2-1 league win over Huddersfield Town on January 11.
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