Steven Pressley and Ferguson both allowed their players to spend Christmas Day off and it was the former who reaped the benefits as the hosts claimed all three points.
The pair showed some Christmas spirit hoping it would give their charges some much-needed rest and it was Coventry who responded with the right result for their boss.
Goals from former Sky Blues youngster Shaun Jeffers and Lee Tomlin sandwiched Leon Clarke's leveller courtesy of a gift from goalkeeper Bobby Olejnik to hand the visitors a 2-1 half-time advantage.
But Olejnik's poor punch gave Clarke a second goal before Franck Moussa and Callum Wilson completed Coventry's comeback.
Posh boss Ferguson said: "We should have been out of sight in the first half. I thought we were outstanding and they could not live with our formation. But for a few mis-placed passes we might have got there.
"The first two goals we gave away were awful and you cannot give goals away like that against one of the best teams in the division.
"But for their 10-point penalty they might be challenging (for promotion) and they yet still might, you never know.
"We knew it would be tough and we knew it would be open but that suited us, but you simply cannot start a half like we did after the break.
"That gave them a lift and for the next 15 minutes or so they created a few chances. I thought we had got through that but unfortunately it did not turn out to be the case."