Newcastle midfielder Jack Colback is being investigated over allegedly breaking betting rules, it is understood.
Gambling rules introduced in 2014 forbid players and coaches from betting on any footballing activity worldwide.
Colback could now face Football Association charges, even though it is understood that the match in which the 26-year-old allegedly broke these rules has no bearing on Newcastle's fight against relegation from the Premier League.
It is FA policy not to comment on such cases until an individual is charged.
But it is understood that the FA is looking into allegations that betting rules have been breached.
Colback has been a regular for Newcastle since joining from neighbours Sunderland in 2014, and played in the club's goalless draw at Aston Villa on Saturday.
Manchester City's Martin Demichelis accepted a charge that he broke betting rules earlier this season.
The Argentina centre-back, 35, was accused of 12 breaches of FA rule E8 concerning matches played between January 22 and 28 this year.