MILLWALL couldn't take maximum advantage after favourable results the previous night as they were held to a draw by Birmingham at The Den on Wednesday.
The Lions created the better chances but couldn't find a way past Blues goalkeeper Lee Camp.
The point moves them to within six of sixth-placed Preston, ahead of Bristol City's visit to The Den on Saturday.
Lions' lost opportunity
Tuesday night's results had presented Millwall with the chance to cut the gap to the play-offs to four points.
But Birmingham were unbeaten in eight league games since New Year's Day, and had lost just once here in their last 11 visits.
The Lions made the energetic start they hadn't in the 1-0 win at Wigan last Saturday, with Mason Bennett prominent, but then seemed to slightly run out of attacking ideas and thrust.
The problem for Millwall when they play 5-2-3 in games like this is the lack of a consistent attacking threat from central midfield. It's where Ben Thompson is missed with his ability to time a run and finish.
The Lions also have three main strikers who are better playing up front with a partner than on their own. Just past the hour Gary Rowett sent on Matt Smith and Tom Bradshaw for Alex Pearce and Bennett.
A combination of those switches and a change of formation to 4-4-2, and knowing they really needed all three points to get back in contact with the top six, prompted more attacking urgency and made them more of a threat to Birmingham's goal.
Despite their improvement this year, and an outside chance of making a late rush for the play-offs, Blues played like a side content in mid-table.
Pep Clotet's team failed to register a shot on target in the game and were pressed back for the majority of the second half.
But it was a case of near-misses for the Lions, not quite getting that vital touch to a cross or not able to get enough players into the box.
It was a feeling of frustration on the final whistle at an opportunity lost.
Bennett makes good first Den impression
The on-loan Derby forward was at the centre of most of Millwall's most positive play early on. Two early crosses from the left led to chances for Jed Wallace and then Jon Dadi Bodvarsson.
He's not afraid to take players on, even when he's deep in his own half facing his own goal. One spin past Harlee Dean drew a foul and relieved the pressure on his side.
There was understandable rustiness. After Jed Wallace's brilliant run down the left he spotted Bennett's run through the centre and found him. But Bennett's first touch was too heavy and the chance was gone.
Given more games that sharpness will come.
Scott Hogan went close to putting the visitors ahead in the second minute when his poked effort went just wide of the post.
Millwall threatened early on from set-pieces and Jude Bellingham was relieved to see the ball go behind for a corner rather than in after he had stuck out a boot from Jake Cooper's header across goal.
It was a good start by the hosts, and Bennett floated a cross from the left that was headed back across goal by Bodvarsson for Jed Wallace whose stabbed attempt was tipped around the post by Camp.
Bennett then hooked another cross over from the left but Bodvarsson flicked a difficult chance wide.
Ivan Sunjic latched on to a poor clearance from Alex Pearce to shoot just wide in the 32nd minute.
Blues thought they had taken the lead when Kristian Pederssen had the ball in Millwall's net five minutes after the break following a corner, but referee David Webb judged Dean had pushed Cooper.
Camp tipped Jayson Molumby's deflected shot around his right-hand post in the 62nd minute and then sprung to his left two minutes later to palm away Bodvarsson's header from Mahlon Romeo's cross.
With 13 minutes left, Romeo went down the right again to cross low and Bradshaw just couldn't stretch enough to make contact with the ball six yards out.
Millwall were committing more players forward leaving Shaun Hutchinson and Cooper exposed and only a vital touch from the latter prevented Hogan getting through, before Marc Roberts was close to reaching Dan Crowley's chip into the box before Bart Bialkowski got to the ball first.
Millwall, to their credit, kept attacking their opponents, but couldn't find a breakthrough.
Rowett made one change from the 1-0 defeat at Wigan, Bennett replacing Bradshaw in attack.
Midfielder Ryan Leonard was out with a hamstring problem, along with Thompson and Shaun Williams, both of whom returned to training this week.
Millwall: Bialkowski; Romeo, Hutchinson, Pearce (Smith, 63), Cooper, M Wallace; Woods, Molumby; J Wallace, Bodvarsson (Mahoney, 80), Bennett (Bradshaw, 63).
Subs: Steele, Ferguson, Smith, O'Brien, Mitchell.
Image: Millwall FC