Graham Westley's men suffer second successive heavy defeat.Peterborough United have shipped seven goals in two Sky Bet League One fixtures as Millwall claimed a comfortable 3-0 success at the Den.
Westley's men were behind thanks to a close-range header from Steve Morison and capitulated in the second period with the home side scoring twice in quick succession from set-pieces.
Posh were restricted to long-range efforts and never really looked like scoring against a Millwall side who were beaten 2-0 by Scunthorpe United on Tuesday night.
Ahead of Tuesday night's fixture with Oldham Athletic at the ABAX, Posh are now nine points behind the Lions.
Striker Lee Gregory saw an early shot blocked by Michael Bostwick as the hosts broke at pace following a well dealt with Posh corner kick at the other end of the pitch.
Jordan Archer made his first save of the afternoon on nine minutes as he pushed a low left-footed drive from Taylor around the post.
On 13 minutes, goalkeeper Archer produced a stunning save with his head to somehow divert an incredibly overhit back pass from Mark Beevers over the crossbar. He quite rightly recieved a superb ovation for his save.
Gregory missed a sitter on 21 minutes as a corner was only half cleared and the ball dropped invitingly for the former Halifax man on the volley, but he blazed over.
On 29 minutes, the home side got their noses in front as Steve MORISON nodded home from close-range after Alnwick had initially saved Gregory's powerful effort.
Coulibaly sent an over head kick wide of the target as Bostwick kept a corner kick alive at the back post. Posh made a double change at the break with Jordan Nicholson and Shaquile Coulthirst introduced for Toffolo and Samuelsen. Nicholson making his first appearance in the Football League.
Coulthirst was lucky to escape with a caution following a very late challenge moments after his introduction. On 49 minutes, the Lions made it 2-0 and it was such a simple goal to try and defend, a lofted free-kick, won by Morrison and there was GREGORY to nod home from close-range past a flat footed Alnwick.
Alnwick was well positioned to claim a Ferguson shot as the home side threatened a third goal. Marcus Maddison replaced Beautyman as Posh made their final change of the afternoon with over half and hour remaining.
Millwall made it 3-0 on 62 minutes as a corner swung in from the left was powered past Alnwick by MORRISON for his second goal of the afternoon.
Maddison saw a curler from 30-yards beaten away by goalkeeper Archer on 66 minutes after good strength from Coulthirst in the build-up.
Coulthirst dragged a shot wide from 20-yards as Posh tried in vain to find a consolation goal. Coulibaly tested Archer from distance with the keeper grabbing the ball at the second opportunity with Coulthirst waiting to pounce.
In stoppage time, Bostwick was given a 10th caution of the campaign leading to an automatic two match ban for obstruction.
Millwall: Archer, Romeo, Webster, Beevers, Martin, Wallace, Abdou, Thompson, Ferguson (sub Onyedinma 85min), Gregory (sub O'Brien 75min), Morison (sub Marquis 72min). Unused subs: Forde, Nelson, Edwards, Powell.
Posh: Alnwick, Smith, Almeida Santos, Bostwick, Toffolo (sub Coulthirsst 46min), Forrester, Beautyman (sub Maddison 56min), Taylor, Samuelsen, Coulibaly, Oztumer (sub Nicholson 46min). Unused subs: Henry, Zakuani, Baldwin, Nichols.
Half-time: Millwall 1-0 Peterborough United
Full-time: Millwall 3-0 Peterborough United
Attendance: 8,722 (763 Posh fans)