The manager was also drenched as he spoke to the press after the final game of a League One promotion-winning season, the victim of a dressing room ambush after the players received their League One runners-up trophy and medals.
Goals from Mo Eisa, Niall Mason, Idris Kanu and Ricky-Jade Jones - his first Football League goal - delivered a 4-0 half-time lead after an outstanding 45-minute display of pacy and powerful football, even though Ferguson made nine changes to his starting line-up.
Posh finished second in League One just two points behind champions Hull City and seven points clear of third-placed Blackpool.
“I couldn’t be prouder of this performance today and of the club as a whole from top to bottom all season,” Ferguson enthused.
“We were absolutely magnificent in the first half. We had pace, power and there was some excellent finishing. The front three all scored and Doncaster couldn’t live with the front two, Idris and Ricky, who pressed and ran hard all game.
“I’ve mentioned how strong and how important the squad is all season so although I made a lot of changes I still expected to win the game.
“We had so many youngsters on the pitch at the end it was very pleasing and very exciting.
“I don’t want to put too much pressure on the lad, but Ronnie Edwards is one of the best young players I’ve ever worked with. I wouldn’t have any hesitation in picking him for Championship matches. Some of those youngsters on at the end will give us good competition for places next season.
“There were players out there who won’t be here next season and they were also excellent and the win and performance were the perfect way to start some more celebrations.
“The players received their medals after the game and there’s no doubt we deserve this promotion. To reach 87 points in such a difficult season is magnificent and we scored 103 goals in all competitions.
“It’s only right you celebrate these victories hard as you don’t know when they will come around again.”
Ferguson handed first-team debuts as second-half substitutes to goalkeeper Will Blackmore, under 18 skipper Charlie O’Connell and 16 year-old forward Adler Nascimento.
Posh are expected to announce their retained list for the 2021-22 season in the Championship tomorrow. Ferguson said there won’t be any surprises.