MILLWALL won successive games for the second time this season as they defeated Nottingham Forest 1-0 at The Den.
Ryan Tunnicliffe gave Millwall the lead in the 10th minute with his second goal of the season.
The Lions rarely looked like they would surrender the advantage despite long periods of Forest possession, and the hosts should have added a second in the last minute but Steve Morison's shot hit the post.
Two wins, two clean sheets, Millwall have made an excellent start to the second half of the season and the players have responded to Neil Harris calling this a "defining" period.
Tunnicliffe took his goal brilliantly and he and Ryan Leonard provided excellent cover in front of their defence to the extent that £13million attacking midfielder Joao Carvalho did very little until he was taken off in the second half.
Millwall then had a different challenge to deal with as Forest changed formation but Jordan Archer only had relatively routine saves to make in the 90 minutes. This was Millwall getting back to scoring once and being confident it would be enough. It was certainly impressive the way late on they frustrated Forest by keeping them penned in their own half.
The only worry was Lee Gregory's departure with an injury 12 minutes into the second half, and there was the frustration that they didn't make it easier for themselves in five minutes of injury-time after Morison's chance.
Nottingham Forest boss Aitor Karanka left top scorer and former Lions striker Lewis Grabban on the bench after a run of four games without a goal coinciding with their winless streak.
Harris named the same Millwall side that won for the first time in nine games when they beat Reading 1-0 on Boxing Day.
In the fourth minute Jed Wallace stood up a cross to the back post but Shane Ferguson needed a few more inches in height as Tendayi Darikwa flicked the ball away.
The Lions were soon ahead and it was deserved as Forest couldn't get out of their own half. Leonard's corner was attacked by Jake Cooper, no Forest player could clear, and Tunnicliffe's overhead kick from six yards went across goal and in off the far post.
Millwall were relentlessly hounding their opponents but Leonard went slightly too far when he caught goalkeeper Costel Pantilimon late and was booked.
Karanka's side had their first shot on target in the 24th minute, Joe Lolley cutting in from the left and his effort was deflected but Archer saved and held on to the ball.
The Lions had Forest in trouble from corners and when Shaun Hutchinson headed towards goal Gregory just failed to make the contact in front of Pantilimon.
A quick Lolley snap-shot tested Archer's reactions and the goalkeeper saved for a corner.
On 33 minutes Wallace flicked the ball to Gregory in the box and when it rebounded to him following his heavy touch Pantilimon saved his poked effort.
Forest had most of the possession without really creating much. Left-back Jack Robinson got forward but headed straight at Archer at the back post.
Forest did settle into the game after a number of loose passes and mis-controls earlier, but the Lions deservedly took that one-goal lead into half-time.
The visitors had the first effort on target after the break through Jack Colback's overhead kick that was straight at Archer. Moments later it was Lolley again showing his threat as he shot just wide from 25 yards.
Leonard wanted a penalty 10 minutes into the second half when he claimed his cross struck Danny Fox on the arm, but referee Tony Harrington didn't agree.
In the 57th minute Harris was forced to bring on Aiden O'Brien for Gregory after the striker needed treatment for a calf problem.
Millwall almost got a second when Forest substitute Adlene Guedioura inadvertently played in Wallace whose shot deflected just over Pantilimon's crossbar.
Grabban came on in the 65th minute for the ineffective Carvalho and was booed by the home fans, as was his every subsequent touch.
But Karanka's side now had someone to run into the wide channels and stretch Millwall, and the stadium was getting tenser as Forest tried to find an equaliser.
Millwall, though, were always tactically disciplined and never really looked like being pegged back. The final whistle was greeted by a great roar at The Den, as the Lions go into 2019 in confident mood.
Image: Millwall FC