The Lions are now just two points off the play-offs with the match against the fourth-placed Swans and a trip to Barnsley on the final day still to come.
"We face Swansea on Saturday in front of what I am sure will be a full house at The Den," said Gallen.
"I am sure Swansea won't fancy that, and if we can take three points then who knows what might happen on the final day of the season?"
Source: PA
Source: PA