MILLWALL lost to Fleetwood Town on Monday afternoon but are still in the play-off places with two games left.
Ben Thompson and Lee Gregory both hit the woodwork in the first half as Millwall dominated.
But Fleetwood worked their way back into the game and went in front in first-half injury-time when Ben Davies headed George Glendon's free-kick past Tom King for what proved to be the winning goal.
Millwall will wonder how they didn't get anything from this game after they had 15 shots on goal and forced 16 corners.
Fleetwood goalkeeper Alex Cairns was named man of the match after making a succession of second-half saves as Millwall lost for the first time in five games.
Southend's defeat at home to MK Dons meant they missed the opportunity to leapfrog their rivals and remain seventh.
Rochdale beat Coventry City 2-0 and Bristol Rovers are only four points behind the Lions after their 1-0 win over Oldham, but it looks like a straight shootout between Millwall and Southend for sixth place.
Millwall were unchanged from the side that defeated Northampton on Good Friday. Shane Ferguson returned to the squad and was on the bench as Jimmy Abdou missed out.
With Bradford losing at Sheffield United in the early League One kick-off Millwall knew they could cut the gap to the Bantams and Monday's opponents to two points with a win at Highbury Stadium.
Thompson went close to giving Millwall the lead in the fourth minute but his shot came of the upright.
Shaun Hutchinson headed over from a corner before Steve Morison saw his volley deflected wide minutes later.
Byron Webster then headed off-target from one of eight corners Millwall forced inside the opening 20 minutes.
Gregory was next to threaten but he shot off the post as Fleetwood continued to survive.
The home side almost went in front in the 33rd minute, but Webster got back to prevent Fleetwood's top scorer David Ball from finding an empty net.
A minute before the break wing-back Conor McLaughlin fired over, before Davies put his side a goal up after Mahlon Romeo had fouled Amari'i Bell.
There was another blow for Millwall when Hutchinson didn't appear for the second half, with Jake Cooper coming on to partner Webster in the centre of defence.
On 53 minutes Wes Burns forced King into a save before Davies rescued his side by blocking Gregory's effort.
King saved again from Bobby Grant in the 64th minute and, a minute later, Cod Army goalkeeper Cairns produced a stunning stop to keep out Cooper's header.
The game continued to be end to end and with 17 minutes left Fleetwood centre-back Nathan Pond sent a volley over the crossbar.
Pond was back on defensive duty to block Aiden O'Brien's shot, and from Millwall's 15th corner of the afternoon Cairns saved from Webster.
In the 83rd minute Grant was put through by Glendon but King got down low to save.
Cairns produced more heroics to deny Gregory with six minutes left as Millwall piled on the pressure.
And the Fleetwood stopper capped a superb display by saving from substitute Calum Butcher in the 94th minute.
It was harsh on Millwall, but they will know it could have been worse and with Southend losing the Lions have their fate in their own hands with two games left.
Image: Millwall FC