Southend boss Paul Sturrock has apoligised to fans for playing Bilel Mohsni, who was red-carded in Tuesday's FA Cup loss at Oldham.
The manager also hinted that a dismal disciplinary record could jeopardise Mohsni's future at Roots Hall.
Southend created the better chances before Mohsni, already on a yellow card, lunged at Dean Furman after 38 minutes and collected his second booking - with the French-Tunisian now facing his third suspension of a season which has also seen him involved in a dressing room fracas in August.
Oldham controlled the rest of the game and, just before the hour, James Wesolowski set up Chris Taylor to lash in from 10 yards and set up a dream third-round tie away to Liverpool.
Sturrock, whose side have now lost three games on the spin after a 17-match unbeaten run, said: "I must apologise to our fans because the situation with Bilel has been ongoing for a long time.
"I have tried to benefit the football club with his ability but it was to our detriment in this game and we are out of the cup. I know there's a footballer in there but Bilel has cost us too many times and this was totally unacceptable. I probably should have taken him off before the red card. He was a walking foul.
"I will debate what happens next with the powers that be. We can't keep having this indiscipline on the pitch. I take responsibility because I pick the team, but it's hard enough beating a League One side with 11 men. The rest of them gave everything and, with 11 men on the pitch, we had most of the pressure. We peppered their keeper, but the sending off was a big lift to Oldham's players."