MK Dons fell to their first defeat in four games after a 2-0 reverse at high-flying Peterborough United.
Two goals in the space of six minutes at the start of the second half ultimately won it for the hosts after an evenly-contested first period.
The Dons rallied and went close through Alex Gilbey, Robbie Muirhead and Osman Sow but they were unable to find a way back into the game, meaning they left the ABAX Stadium empty-handed.
Dean Lewington was recalled to the starting XI as Robbie Neilson changed to a 3-5-2 formation, while there was a welcome return to the substitutes’ bench for Chuks Aneke after six months out.
The first real action of the evening saw Aaron Tshibola drive forward from midfield before his shot was deflected into the arms of Jonathan Bond.
Peterborough’s opening opportunity came from a Gwion Edwards cross but the Dons managed to clear prior to, at the other end, Ryan Seager curling an effort over the top from 15 yards.
Both sides were looking dangerous going forward – Scott Golbourne was unfortunately offside for the Dons after some smart build-up play while Nicholls made a strong save away to his left to deny Edwards from the edge of the area.
Shortly afterwards, Ryan Tafazolli headed a left-wing corner past the post and Nicholls, who denied Marcus Maddison just before the half-hour mark after the winger had cut in from the left.
Former Newcastle United defender Steven Taylor directed an effort off target after Lewington had picked up good positions to avert the danger on two occasions.
Tshibola sent a 25-yard drive narrowly over Bond’s bar with just over 10 minutes remaining of the first half before long-range shots from Gilbey and Edwards were well saved by the respective keepers.
The Dons survived a scare on 39 minutes when a right-wing corner wasn’t comfortably dealt with although Brittain was down injured, suggesting there may have been an infringement.
With the half drawing to a close, Tshibola made good yards but his pass to Golbourne left the wing-back a little short and a promising attack was ended – the midfielder was impressing in the centre of the park though.
The hosts hit the front two minutes into the second half when, despite it looking like Nicholls was being fouled, the referee allowed Tafazolli’s header from Maddison’s corner to stand.
Nicholls saved Edwards’ shot shortly afterwards as Peterborough tried to double their advantage while, at the other end, Gilbey almost caught Grant McCann’s men on the counter but his touch was too heavy.
Provider for the first scored the second six minutes later as Maddison curled home a fine finish from 20 yards after the Dons had given up possession too easily in midfield.
Neilson responded with a triple substitution as Muirhead, Aidan Nesbitt and Sow entered the fray for Kieran Agard, Lewington and Seager.
However, it was one of the starters – Gilbey – that threatened the hosts’ goal on the hour mark but his 20-yard effort deflected over the top – from the resulting corner, Muirhead was denied at close range.
Gilbey again found some space three minutes later but, after turning his man, his low drive was blocked – the Dons reacted in the right manner following a lacklustre start to the second period.
While the men from MK1 looked for a way back into the game, Nicholls ensured it remained 2-0 with a smart double save to deny to Jack Marriott and Ricky Miller.
Nesbitt couldn’t pick out a team-mate with a left-wing cross as the game approached the final 15 minutes – the Dons needed a goal to give themselves hope.
That nearly came a few minutes later but Sow’s shot was brilliantly blocked before Tafazolli’s clearance almost put his side in danger, but Bond was able to gather.
Gilbey continued to look the most likely player for the Dons and he teed up Nesbitt, who saw his shot saved by Bond from the edge of the area.
Dons’ No. 26 then forced a fine save from Bond on 84 minutes before Nicholls made an even better stop to deny Leo Da Silva Lopes after a purposeful run from the young midfielder.
Birthday boy Scott Wootton went incredibly close to reducing the arrears in the final minute of normal time but his header was superbly saved – the rebound was cleared away, denying the chance of a grandstand finish.
Starting XI: Nicholls; Williams, Wootton, Lewington (c) (Nesbitt 56); Brittain, Cisse, Gilbey, Tshibola, Golbourne; Seager (Sow 56), Agard (Muirhead 56).
Unused subs: Sietsma, McGrandles, Ariyibi, Aneke.
Attendance: 6,465 (369 Dons fans).