Milan Lalkovic scored his seventh goal of the season as Walsall beat Millwall to go top of League One.
The Saddlers dominated the first-half and took a deserved 29th-minute lead when Lalkovic coolly slotted past Lions keeper David Forde.
Millwall rallied late on with Aiden O’Brien hitting the bar, but the visitors defended manfully to secure a fourth consecutive league win.
Walsall have now taken 45 points from 22 league matches and are above second-placed Burton on goal difference.
Head coach Sean O’Driscoll named an unchanged team for the Saddlers’ first visit to The Den since January 2010.
Walsall – boasting the division’s best away record – settled quickly into their passing rhythm and dominated possession in the early stages.
Their first attempt came on four minutes, George Evans playing a neat one-two with Romaine Sawyers before firing over from distance.
The visitors threatened again shortly after with James O’Connor directing a header straight at Lions keeper David Forde from a corner.
But Millwall, who were relegated from the Championship last season, should have taken the lead after 21 minutes.
Fred Onyedinma’s low cross-shot squirmed through to Steve Morison, who - just six yards out - could only find the side-netting.
Saddlers stopper Neil Etheridge was then called into action when he pushed away O’Brien’s stinging drive from an acute angle.
After surviving those scares, Walsall went ahead on the half-hour mark.
Sid Nelson misjudged a long ball, allowing Lalkovic to nip in behind the home defence and coolly slide a right-footed shot past David Forde.
The Saddlers were far superior in a one-sided first-half and could have increased their advantage before the break.
On 42 minutes, Walsall counter-attacked at pace with Anthony Forde finding Sawyers, who cut the ball back for Lalkovic to side-foot over.
The visitors threatened again moments later, Anthony Forde gliding past Edwards before seeing a placed effort saved by his namesake David.
HALF-TIME: MILLWALL 0-1 WALSALL
Walsall continued to look dangerous after the break, with Lalkovic cutting in from the right before testing David Forde with a low drive.
But a direct Millwall side were much improved in the second half and began to impose themselves on proceedings.
And Neil Harris' Lions came mightily close to forcing an equaliser on 54 minutes.
Morison’s hooked cross was met by O’Brien, who looked certain to score, but Etheridge made a remarkable point-blank save to turn the ball away.
The hosts continued to cause problems but Walsall were defending resolutely.
O’Connor produced an immaculately-timed last-ditch tackle to dispossess Onyedinma and O’Brien then fired wide from a tight angle.
Walsall captain Adam Chambers, who was outstanding throughout, also made a heroic block from Ed Upson’s fierce goalbound shot.
The Saddlers were subdued going forward in the second-half, with Evans dragging a 25-yard effort wide on a rare foray into Millwall territory.
And Walsall were pushed back in the closing stages as Millwall launched an aerial bombardment.
Shane Ferguson’s cross was headed onto the bar by O’Brien and Morison's glancing header forced a fine reaction save from Etheridge.
But the visitors held on to make it back-to-back wins - and clean sheets - under new head coach O'Driscoll.
FULL-TIME: MILLWALL 0-1 WALSALLTeam:
Etheridge, Demetriou, Taylor (Kinsella 45’), Downing, O’Connor, Chambers, Evans, Sawyers, Forde, Morris (Cook 72'), Lalkovic (Preston 89').
Subs not used: Roberts, Mantom, Baxendale, Flanagan.
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