Two Keith Andrews penalties and strikes from Benik Afobe and Martin Petrov weren’t enough, as Wanderers were edged in a nine-goal thriller at rain-soaked Peterborough.
Dougie Freedman kept the same 11 that started last weekend’s 2-0 home win over Charlton Athletic, as Wanderers returned to London Road for the first time since 1994.
Lee Tomlin gave the home side an early lead on two minutes, after he was sent clear and calmly stroked the ball into the far corner of Adam Bogdan’s net.
Three minutes later Bogdan was forced into an exceptional, point-blank save to deny Tomlin’s strike partner Dwight Gayle.
With six minutes played, the hosts doubled their advantage. The ball again fell to Gayle in the middle of the area, and the striker managed to shoot on the turn, finding the top corner with a powerful finish.
And eight minutes later, Tomlin went close to getting his second and Peterborough’s third. The frontman was able to wriggle free of several challenges and hit another curling shot towards the bottom right-hand corner, only to see his effort come back off the post.
Despite very few clear-cut chances in the opening 45, Wanderers were given a route back into the game in first half stoppage time, when, from a Jacob Butterfield corner, Sam Ricketts was wrestled to the ground and the referee awarded a penalty.
Andrews stepped up and dispatched a powerful strike to the left of Bobby Olejnik.
But having halved the deficit seconds before the break, Wanderers again found themselves trailing by two on 47 minutes, when George Thorne fired in a low shot from the edge of the area.
Freedman reacted by making a double substitution, replacing Butterfield and Chung-Yong Lee with Afobe and Marvin Sordell.
And after just five minutes on the pitch, Afobe earned Wanderers their second penalty of the afternoon, out-muscling his opponent and drawing the foul. Andrews again confidently fired in the spot-kick to make it 3-2.
But Peterborough restored their two-goal cushion on 69 minutes, when a cross towards the far post was met by Mark Little, who fired past Bogdan.
Andrews almost responded for a third time two minutes later, and was denied a hat-trick after seeing his thunderous shot towards the top corner superbly saved by Olejnik.
And with 82 minutes played, Gabriel Zakuani increased the hosts’ lead, heading in from Tomlin’s floated corner to make it 5-2.
Benik Afobe hit back a minute later with his third of the season, also connecting with a header from a corner, after Olejnik had produced another wonder save to flick a thumping Petrov volley behind.
With three minutes left of the 90, Petrov gave the Whites hope of a remarkable comeback, blasting the ball high into the roof of the net after being cleverly played through by Sordell.
But it wasn’t to be, as Peterborough resisted Wanderers stoppage time efforts to earn a 5-4 victory.
Peterborough: Olejnik, Little (Alcock 88), Bostwick, Zakuani, Knight-Percival, Rowe, Thorne, Newell (Ferdinand 80), Boyd, Tomlin, Gayle (Unused subs: Day, Brisley, Swanson, McCann, Kearns)
Wanderers: Bogdan, Mears, Knight, Ricketts, Warnock, Spearing, Andrews (Petrov 80), Lee (Sordell 50), Butterfield (Afobe 50), Eagles, K. Davies (Unused subs: Lainton, Alonso, Ream, Pratley)