Carlisle midfielder Liam Noble faces internal disciplinary action over comments he posted to Sunderland fans via Twitter.
Noble, 20, has also been warned about his future conduct by the Football Association following an exchange with supporters from his former club.
A Carlisle statement read: "Carlisle United Football Club can confirm that midfielder Liam Noble has faced internal disciplinary action for comments made on the social networking site Twitter earlier this week during online conversations with fans from his former club, Sunderland AFC.
"The FA have also written to Mr Noble about the incident and the club and player are co-operating fully with their requests.
"The club can make no further comment until this process is complete."
Noble made 24 appearances for the Cumbrians while on loan from Sunderland last season and after extending his stay during the first half of the current campaign, he made the move permanent during the January transfer window.