All you need to know about Saturday's game
Having lost all four of their opening League One matches on home soil this season, The Lions have rediscovered that winning touch in SE16 with consecutive wins against Rochdale (3-1) and Northampton (2-0).
The Lions may be the bookies favourites to see off a Swindon side that have lost six of their last seven starts, including a 2-0 JPT defeat at Oxford United, but The Robins will have revenge firmly in mind having lost out on the chance of a place in the Championship when the two teams last met in the 2009/10 League One Play-Off Final.
What the managers say
"That performance and result came on the back of our frustration at what happened against Peterborough United. We played really well there and bossed the game for large periods, but managed to let five goals in.
"We will have to be at our best to make sure we put in a performance and get the points."
Mark Cooper: "We have got a lot of players unavailable at the moment and until we get them back it's going to be hard. It is difficult when you're having to play different players every week and until you get a settled team it's difficult to get anything set in stone.
"You come back to the fact that you've got so many of your better players unavailable, until they get back fit it is going to be difficult. Somehow we have to scramble a result from somewhere."
Williams missed The Lions' last game before the international break, a 2-0 JPT win against Northampton Town, having picked up his fifth booking of the season the previous Saturday at Peterborough United.
But having served his one-match suspension Williams is now available for selection to boost a midfield depleted by the continued absence of Jimmy Abdou (shoulder) and Ed Upson (knee).
Saturday's Den encounter could also see recent signing George Saville make his first League start for The Lions having signed on loan from Wolves hours before making his debut in the JPT game with Northampton.
Winger Paris Cowan-Hall has made solid progress from a groin injury sustained playing for the U21s last September, but Saturday's game could be just a tad too soon to be considered for selection.
Swindon manager Mark Cooper is facing something of an injury crisis with striker Jermaine Hylton this week becoming the latest player to be consigned to Town's treatment room after picking up a groin strain in training.
Louis Thompson, Jon Obika, Nathan Thompson, Jordan Turnbull, Wes Thomas, Jordan Williams, Kevin Stewart and Fabien Robert are already ruled out whilst a late decision will be made on the availability of Brad Barry, Yaser Kasim and defender Rafa Branco.
On that historic occasion in May 2010 Lions skipper Paul Robinson lived up to his name of 'Captain Fantastic' by scoring the only goal of a tense League One Play-Off Final as Millwall sealed their return to the Championship.
Overall in the previous 92 matches, Millwall have won 36 with 27 games drawn and Swindon victorious in the other 29 fixtures.