London - Barnsley's Bambo Diaby is the subject of a Football Association probe over a potential doping violation.
The 22-year-old defender is reported to have been tested following the Championship team's match at Blackburn in November.
"Barnsley Football Club have received notification from the FA that they are investigating a potential anti-doping violation by our player, Bambo Diaby," a Barnsley statement said.
"The player and club are cooperating and responding directly with the FA. The player is now subject to a playing suspension whilst this matter is under investigation."
Barnsley manager Gerhard Struber admitted Diaby's situation had been a distraction for his struggling side ahead of their defeat against Preston in the second-tier Championship on Tuesday.
"It was distracting. The process is running but it's not the right time to speak about Bambo," he said.
The Senegalese player, who joined Barnsley last year from Belgian club Lokeren, has started 21 of the club's 29 Championship matches this season.
A positive test for a banned substance that is on the World Anti-Doping Agency's prohibited list can lead to a four-year suspension.