Paul Robinson's appeal against the red card he received at Oldham on Saturday was rejected at an FA hearing on Tuesday afternoon.
The Lions skipper now serves a one match suspension, missing tonight's Carling Cup First Round tie against Northampton Town at The Den (7.45pm).
He is available again for the visit of Southend United in League One this weekend.
Robbo said: "Naturally I'm disappointed because it was a very harsh decision, but I'm confident the lads will put in a good performance this evening and we can progress through to the Second Round."
Andy Frampton, who came on as a late substitute at Boundary Park is likely to deputise for the skipper.