The final month of 2017 began with the news that defender Shaun Hutchinson had extended his contract at The Den until the summer of 2020.
"Since I came to this club I have always enjoyed my time here," he told millwallfc.co.uk. Working with the gaffer and the lads has helped me to settle here and I do believe this manager has created a team that can bring success."
Sheffield United were the visitors to SE16 the next day and The Lions turned on the style to claim victory.
Lee Gregory notched his third goal of the campaign to open the scoring, but David Brooks equalised for The Blades shortly before the half-time break.
However, a superb piece of play from Gregory to win the ball back in the centre-circle on 66 minutes allowed Mahlon Romeo - in for the suspended Conor McLaughlin - to score his first goal of the season on his first Sky Bet Championship start.
Jake Cooper crashed a header home off the crossbar late on to add the gloss to a fine performance.
"At half-time, my staff and I had a conundrum - do we leave it as it is, or do we change it," Neil Harris told millwallfc.co.uk. "We made a brave decision and changed to a 3-5-2 to match up with them and I thought the players were outstanding. They're never going to let me down on effort and determination, plus the desire to play for this club. They're never going to shirk a challenge."
A daunting looking trip to Villa Park followed a week later, but an impressive Lions performance grabbed a point in a goalless draw - but it could have been much more.
"I thought the team was outstanding from the first whistle to the last. We unsettled a very good Aston Villa side," said the manager.
"We quietened down a passionate crowd for large parts and dominated the game. We limited Villa to having very few chances on goal all game and then we've been really creative going forward.
"We had passion, quality, challenges - everything you expect from a Millwall team was there."
Steve Morison triggered a clause to extend his contract shortly before Middlesbrough visited The Den on 16th December and The Lions extended their unbeaten run at home courtesy of goals from Jed Wallace and George Saville in a 2-1 win.
The former Wolves duo put Millwall two goals up, but Stewart Downing's consolation ensured a nervy finish. The beaten Play-Off Semi-Finalists battled hard to find the equaliser, but The Lions' defence stood firm to claim all three points.
The Christmas period began at Derby County on the 23rd and despite a performance worthy of securing a first away win of the season, five minutes of madness ensured The Lions returned home pointless, losing 3-0. David Nugent (2) and Matej Vydra were on target shortly before the half-hour mark.
Harris explained how the defeat was a 'reality check.' "I've reminded the players that if anyone was getting a little ahead of themselves after seven points from the last three games, that's a reality check. We'll take that on the chin, re-build and move on to Wolves on Boxing Day."
A Christmas cracker was served up as the League leaders were held to a 2-2 draw at The Den, as goals from Gregory and Cooper sandwiched strikes from Diogo Jota and Romain Saiss.
The last game of 2017 was the much-awaited visit of Queens Park Rangers. Courtesy of Steve Morison's first goal of the season - a header at the back post from Wallace's cross on 55 minutes - The Lions claimed victory and ended the year in 15th position.
The manager was full of praise for his goalscorer after the game.
"Steve's performances and leadership qualities have been outstanding. He gets embarrassed with the praise I've given him in front of the players over the years, but you're never too grey or too old to get that kind of praise from your manager. The goal has been a long time coming and his performances have warranted a starting place. He showed that tonight."