#1: Webster bounces back from Reading disappointment
Ian Holloway was the first to admit that the circumstances of Byron Webster's substitution against Reading last month would have knocked the confidence of any player.
The centre back, making his league debut for the club, was hooked off after just 26 minutes to accommodate a tactical switch with the Lions 2-0 down.
Holloway claimed Webster took the decision in "fantastic spirit" but, on the inside, he would surely have felt like a scapegoat as he trudged to the touchline.
It was a nightmare start to Webster's Championship career with Millwall.
So when he was recalled to the starting XI on Saturday, Webster had a point to prove – and there couldn't have been a better platform for him to do so than against third-placed Derby.
The Rams had already hit 18 goals this season (compared to the Lions' ten) and have been in particularly ominous form at home, where they've lost just twice under Steve McClaren.
It was a big opportunity for Webster to get back on track and he seized the opportunity with both hands, producing a commanding and composed performance.
Webster struck up an immediate understanding with Millwall's other centre back on the day, Shaun Williams, who was a calming influence at the heart of the defence.
Between the two of them, Williams and Webster made seven tackles, three interceptions, 14 clearances and three blocks as Derby's sharp forward line was blunted.
Webster will be relieved that his second league start for the Lions lasted longer than his first – but he can also be proud of a resilient display and a hard-earned clean sheet.
#2: Briggs passes test of character with flying colours
When Matthew Briggs first joined Millwall on trial in the summer, Ian Holloway expressed niggling doubts about the left back's mental strength.
"If I bring someone to my club who might not start well and then cannot handle it, then I'm wasting my chairman's money," Holloway said, before handing the ex-Fulham star a deal.
Briggs' career at The Den started well enough. 27 minutes into his debut against Wycombe, he scored what proved to be the winning goal in the first round of the Capital One Cup.
But in the same game, and having been booked for removing his shirt in celebration, Briggs was shown a second yellow card and consequently a red.
Were Holloway's fears about the defender coming true already?
After serving a one-match suspension, Briggs was recalled for the second round tie against Southampton. He had a quiet game, was booked again and hadn't been seen since.
So like Webster, Briggs needed to lay down a marker against the Rams. This was his league debut and the first time he had been picked ahead of Scott Malone in the Championship.
Briggs was lucky to escape an early yellow card for a raking lunge on Chris Martin but, after that rash tackle, he really grew into the game and was effective at both ends of the field.
He made more tackles than any other Millwall player and used his strength and speed to get up and down the left flank, troubling Derby's back four with a couple of mazy runs.
He was also inches away from scoring with a left-foot rocket that arced narrowly wide of the bottom corner.
But what stood out the most – and will have pleased Holloway more than anything – was Briggs' defensive discipline against a very dangerous opponent.
The former England U21 international proved, in the face of mounting Derby pressure in the second half, that he can stand up and be counted when the going gets tough.
#3: O'Brien a threat on first Championship start
Aiden O'Brien made a big impact when he came on against Birmingham last Tuesday.
That impressive substitute appearance was his first in the Championship – and it was rightly rewarded with a full league debut at the iPro Stadium.
And on what was his 21st birthday, O'Brien came of age.
Switching between the left and the right wing, he offered a real threat on the counter attack and put in the necessary defensive work too, which isn't always true of a young player.
He was efficient with the ball (completing 80% of his passes) and created two chances – one for Lee Gregory, whose shot was blocked, before his own drive was deflected for a corner.
O'Brien nearly chalked up his second assist of the week with a dangerous low cross to the back post which was whipped away from Gregory's toes by a defender at the last second.
It was a really promising performance.
When Holloway discusses the youngsters on the fringes of his squad, O'Brien is spoken of in the same terms as Fred Onyedinma and Sid Nelson – even though he is several years older.
So by O'Brien's own admission, he has reached the make or break, sink or swim stage of his Millwall career after working his way up through the academy ranks.
Now that he has finally broken into the Lions' senior side, O'Brien will be desperate to stay there. And he did more than enough against Derby to warrant another start.
#4: Holloway wins tactical battle to frustrate Rams
Derby fans have accused Millwall of playing anti-football.
But before they start complaining about the Lions' defensive display, perhaps they should question why their side could only muster one shot on target.
In fact, the visitors had more efforts on goal than Derby did (11 compared to ten) and two of those forced Lee Grant into making saves, albeit routine ones.
Likewise, David Forde's only stop of the afternoon was a two-handed parry from Jamie Ward's 20-yard drive. Frankly, neither side created enough clear-cut opportunities.
But Millwall would have been asking for trouble if they had opened up and tried to beat the Rams at their own game. That almost certainly would have ended in a defeat.
Bolton tried to "out-football" McClaren's side last week and ended up losing 2-0. Their then manager, Dougie Freedman, paid for that tactic with his job just days later.
So Holloway set his side up not to concede and he was absolutely right to do so because the Lions desperately needed a positive result before the international break.
If Derby want to be promoted to the Premier League, they will first have to find a way of breaking down stubborn opponents.
And their fans should learn to recognise a brave performance when they see one.
#5: Break has come at the perfect time for Lions
Millwall need to regroup so this international break is perfectly-timed.
And thankfully the Lions don't have another loss to stew on before their next game against Wolves in a fortnight's time. A point at Derby gives them something to build on.
When the Championship took two weeks off at the start of September, Holloway's men were building up a head of steam but a bit of downtime took the wind out of their sails.
This time around, however, the break will work in Millwall's favour. By the time the games resume again, Lee Martin should be able to return from a knee injury.
And Holloway can now afford to focus more of his attention on exploring the loan market for possible additions to his squad.
But more importantly, the Lions manager will spend time with his players on the training ground ironing out the defensive frailties that have emerged during the past month.
Millwall have long had difficulty scoring goals but, as their performance at Derby proved, they can be much tighter at the back and that has to be Holloway's top priority.