His opposite number Darren Ferguson worked wonders with his half-time team talk as Peterborough broke the deadlock just 30 seconds after the break.
The Macclesfield defence failed to clear a Chris Whelpdale long throw and George Boyd was first to react running across the face of goal before clipping a shot on the turn in off the far post.
Worse was to follow for the home fans as Whelpdale unleashed a superb 20-yard drive that curled into the far corner in the 64th minute.
The game was sealed in the 72nd minute when live-wire striker Aaron McLean outwitted Luke Dimech to race onto a Chris Westwood long ball before burying his 27th goal of the season from 15 yards.
Peterborough might have added a fourth at the death as Liam Hatch broke past the defence only to shoot wide from a narrow angle.
The Posh had also dominated the first half with midfield man Charlie Lee shooting inches over the bar from 15 yards in the 15th minute. Macc keeper Jonny Brain also had to make two stunning saves to deny long-range efforts from Boyd.
It was Macclesfield's fifth successive home defeat and they have now failed to win in nine games leaving a huge question mark over the future of boss Brightwell.