Scotland international defender Phil Bardsley has been suspended by Sunderland, reports BBC Newcastle.
The 28-year-old is believed to have mocked the Black Cats' opening-day defeat by Fulham on social media.
Bardsley, out with a broken foot, has not been involved with the first team or given a squad number this summer.
Manager Paolo Di Canio has previously been
critical of the former Manchester United player,
after he was pictured in a casino at the end of last season.
Until that incident the former Aston Villa and Rangers loanee had been a regular, playing five of six games under the Italian before he was dropped for the final match of the season at Tottenham.
Sunderland, who handed Bardsley a
at the Stadium of Light in November 2010, which expires in 2014, are believed to be investigating the incident.