Millwall returned to Sky Bet Championship action after the international break with a 1-0 defeat at champions-elect Wolverhampton Wanderers.
In another game where The Lions more than matched their opponents they had to make do with 10 men for the final 25 minutes after Aiden O'Brien was sent off for two bookable offences.
"I'm absolutely delighted with the determination, the passion, the spirit and the character that we showed. We showed great shape with 10 and 11 men," said Neil Harris shortly after the loss.
Millwall were reduced to 10 for the second successive game on 12th September as Lee Gregory was sent off in a topsy-turvy 2-2 draw at Queens Park Rangers.
It looked as though The Lions were on their way to that elusive first away win once Conor McLaughlin scored a Goal of the Season contender inside six minutes, but Gregory's red card - which was appealed against but rejected - threatened to derail Millwall's charge.
However, Jed Wallace broke free and extended the lead five minutes into the second half, sparking wild celebrations in the away end at Loftus Road.
But, as hard as the depleted Lions tried to hold on to their lead, the QPR barrage was too much as Massimo Luongo and Matt Smith both scored to secure a 2-2 draw.
Harris felt a sense of pride, but also disppointment, after the game.
"It's a good point. I'm really proud of the character and the performance. For 40 minutes, at 11 v 11 - what a great away performance. "It's a good point, but I'm disappointed for my players that we couldn't see the game out."
Next up was the visit of unbeaten League leaders Leeds United to The Den.
The home side overpowered their rivals from start to finish, with O'Brien's strike securing Millwall their second Championship win of the campaign.
In one of The Lions' best performances of the season, the manager revealed how much work had been done behind-the-scenes to secure such a result.
"We knew it was going to be tough. Leeds are top of the League and have scored the most goals and conceded the least. We worked very hard on Thursday and Friday to make sure the team had the gameplan right - credit goes to the players for executing it. We out-fought and out-run Leeds and won every first and second ball."
A second successive draw on the road was gained in a war of attrition at Preston North End the following Saturday. In a game where defences were on top, the club stretched their unbeaten run to three matches ahead of a Den double-header against Reading and Barnsley.
It looked as though the run was coming to an end as David Edwards gave The Royals a 73rd-minute lead, but George Saville - recently called into the Northern Ireland squad - hit two late goals to turn the game on its head and hand Millwall all three points.
"Beating Norwich, Leeds and Reading - three big clubs at this level - show we deserve to be here," said Harris following the win over Jaap Stam's men, but September ended on a sour note as Barnsley took a 3-1 win away from SE16, with Gregory's penalty-kick the only positive.
"We were too stretched and we gave the ball away too much. Ultimately, if you give good players at this level those opportunities, they're going to take them. Barnsley deserved to win the game because they took their chances."