Southend's Harry Lennon has been made to train with the club's under-23 squad after being filmed out with Dover players after Sunday's FA Cup defeat.
A video on social media showed the centre-back, 24, in a pub wearing his Southend tracksuit hours after they had lost 1-0 at National League side Dover.
Sol Campbell's Shrimpers are 22nd in League One, with only two wins in 22 games this season in all competitions.
Ex-Charlton defender Lennon has made 18 appearances for the club in 2019-20.
'Adding fuel to the fire' - Analysis
Glenn Speller, BBC Essex sports editor
Lennon's actions outraged Southend fans who took to social media to voice their anger at the defender's actions.
It's added fuel to the fire, with the Blues in the midst of their worst ever start to a season, knocked out of the FA Cup by non-league opposition and having lost all four games under new manager Campbell.
If he does return to the first team, he can expect a rough ride from a Blues support whose patience snapped after Sunday's defeat by Dover as they let the players know of their displeasure in no uncertain terms.
This latest incident has left many supporters wondering if this is rock bottom of a miserable season which has also seen the club issued with another winding-up petition by HM Revenue & Customs.