Veteran striker Steve Claridge kept Millwall on course for a play-off place with a brace in a 2-0 win over relegation-threatened Grimsby at Blundell Park.
Claridge, whose double earned his side a 2-0 victory when the teams met at The New Den in August, pounced from close range two minutes before half-time after Dennis Wise had seen his shot parried by goalkeeper Danny Coyne.
It was his fourth goal in as many games - and 10th of the season - and it arrived just five minutes after Republic of Ireland international Steven Reid hit the Mariners' woodwork.
Claridge, himself, crashed a second-half shot against the frame of the goal as Millwall dominated the second half.
But he sealed the points for the visitors eight minutes from time when he converted a penalty after Reid had been fouled by Grimsby defender John McDermott.
It was a totally different story in the first half when Lions goalkeeper Tony Warner pulled off a string of fine saves to deny Grimsby a deserved lead.
The Mariners, unbeaten in their last four league games, nearly made the best possible start.
Player-manager Paul Groves, making his 425th appearance for the club to put him fourth in the all-time list, steered a header on target but Warner tipped the ball over.
A minute later Simon Ford, back in the side after being rested for the 4-0 FA Cup third-round replay defeat at Burnley in midweek, unleashed a shot which Warner also saved.
Millwall, who scraped past Third Division Cambridge via an FA Cup replay, just could not get going and Town's Stuart Campbell fired wide as the hosts continued to press.
Warner needed to be on his toes again in the 13th minute when Campbell drilled in another shot and from a free-kick, Darren Barnard was this time thwarted by the former Liverpool stopper.
It took Millwall, seven points off the play-off zone, 20 minutes to register their first attempt at goal, Claridge seeing his effort comfortably saved by Coyne.
However, Millwall were unlucky not to take the lead seven minutes before the break.
Reid unleashed a fine shot from 25 yards which crashed against the woodwork before Claridge edged his side ahead.
Grimsby had a let-off 20 minutes from time when Claridge saw his speculative shot rebound of the woodwork.
But he did add his second from the spot to leave Grimsby one place and point above the drop zone.