Pierre-Emile Hojbjerg apologised to Southampton supporters following his red card in Sunday's 3-1 defeat to Manchester City.
Hojbjerg had earlier scored Southampton's equaliser after David Silva put City ahead in the Premier League fixture – the Denmark international beating Ederson with an emphatic drive.
But James Ward-Prowse's own goal and a Sergio Aguero header before the break ultimately gave Southampton too much to do.
Hojbjerg was then shown a straight red five minutes from the end for a wild lunge on Fernandinho, meaning he will serve a third suspension this season.
In a statement released on Saints' Twitter account, the midfielder said: "I would like to apologise about my red card and letting my team-mates down.
's Pierre-Emile Højbjerg apologised after his dismissal against this afternoon: December 30, 2018
"Sometimes my passion takes over my control, but I will work hard on this and I'm focused on coming back stronger.
"The support was great again and we must keep pulling together in one direction to reach our potential."
Saints boss Ralph Hasenhuttl admitted his team had no intention of going all-out in search of an unlikely comeback in the second half, knowing they risked conceding further goals and losing heavily against the champions.
"At the break we made the decision that we don't go all in and take too much risk," the Austrian said.
"We wanted to show in the second-half that we can defend and not to lose the second half, if you want.
"Then, maybe you get a second goal and I think we have one header off a free-kick which could have given us a chance to come back.
"The substitutions I made were very focused on the Chelsea game. The worst moment of the evening was the red card for Pierre, because on 85 minutes the game was gone and it was silly, which he knows. It could cost us a lot."
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