All you need to know about Tuesday's game
The Lions' last four trips to The Seasiders have ended in bitter disappointment with 'Pool edging to victory by a solitary goal on each occasion.
You have to go back to February 2007 and a stunning volley from Dave Brammer to find the last time Millwall collected all three points at Blackpool.
However Harris' charges go into action in upbeat mood after responding positively to that 5-3 defeat at Peterborough United - the first away loss of the season - with two clean sheets in subsequent matches against Northampton and Swindon Town.
Blackpool have picked up considerably since the start of the season and having lost their first three games at Bloomfield Road, have now not been beaten on home soil since a 4-0 thumping by Walsall at the tail end of August.
Neil McDonald's charges have won three out of their last four fixtures, including successive home victories against Chesterfield (2-0) and Swindon Town (1-0), having also recorded an excellent 0-0 draw at Coventry City three days ago.
What the management says
"It's going to be a tough one. We have watched a few of their games, they are organised and in some respects will be tougher than Swindon were on Saturday. All we can do is look after ourselves, make sure we are ready, make sure we are prepared and hopefully get a positive result."
Blackpool manager Neil McDonald: "We should have won the game against Coventry and created six really, really good chances. Defensively we were very solid, worked hard for each other and did enough to win.
That could mean a first away start in the League for striker Lee Gregory since the 2-2 draw at Wigan in September. Last season's top scorer has bagged a goal in each of Millwall's last two matches against Northampton Town (2-0) and Swindon (2-0) to take his tally this campaign to four, one shy of Aiden O'Brien who has five goals to his credit.
The Lions have no fresh injury worries.
Blackpool bolstered their defensive ranks by snapping up Hayden White on loan from Bolton Wanderers on Monday morning and the 20-year-old will remain at Bloomfield Road until January.
The right-back trained with his new team-mates minutes after penning his loan deal and is expected to go straight into the squad to face Millwall on Tuesday night.
White has made five first-team appearances for Bolton and has also previously spent time out on loan with Carlisle United, Bury and Notts County.
'Pool reported no new injury concerns following their 0-0 draw at high-flying Coventry City on Saturday in a match that saw fit-again Henry Cameron return to the starting line-up after missing the previous outing against Port Vale, and keeper Kyle Letheren named on the bench.
The last time the two teams met came back in January 2015 when Peter Clarke's first goal since October 2011 gave bottom-of-the-table Blackpool a 1-0 victory.
The Lions are looking to make it three 2-0 wins in a row and Sky Bet offer 9/1 for a 2-0 success to the away side at Bloomfield Road.