"If I'm honest the game looked like it was going to go to a replay but it didn't and we're hugely disappointed," Stimson told BBC Radio Kent.
"The reward is massive and for us not to be playing Fulham on Saturday is a massive blow."
The 1-0 defeat at Accrington means the Gills are still without an away win all season, something Stimson says he will now address by bringing in new players.
"I think there are one or two new faces needed because we've given these players time to get results away from home and they haven't delivered," said Stimson.
"They have at home but we might need a different clientele away from home to be a bit more ruthless.
"I just think that we need to freshen it up, not to put pressure on players, but we might need a few new faces to let them know they'll only play every week if they perform."
Meanwhile, Stimson has confirmed that striker Febian Brandy has turned down the chance to extend his loan deal at Priestfield and has instead returned to Manchester United.
Source: BBC Sport
Source: BBC Sport