Some 48 hours later, pre-occupied by a match against Chelsea over the coming weekend, Mancini played a greatly reduced team at West Bromwich Albion in the Carling Cup, lost 2-1, and a noted firm of turf accountants in my high street grew ever so slightly richer.
Platt was not wrong, though. The fixtures may have compromised Mancini in the midweek competition, but to those who know him well, this FA Cup victory will have come as no surprise. Throughout his professional career, as player and now as a coach, Mancini has used cup tournaments as a galvanising force, a springboard to improvement.
Raised in a football culture that does not value the Coppa Italia, Mancini always had a different attitude.
Cup King: Roberto Mancini lifts the FA Cup
Perhaps this came from playing the bulk of his career at Sampdoria, a club whose best league finish when he joined was second place in 1922. With history against him, cup football became special to Mancini. Sampdoria did ultimately win their only league title with him in the team in 1991, but central to building that success were Coppa Italia victories in 1985, 1988 and 1989.
It was there that the young Mancini saw how, at a club outside the elite group, the smaller tournaments represent an opportunity to achieve, and how this can then be fashioned to inspire greatness. It was a pattern that has been followed throughout his management life.
Proven pedigree: Mancini lifts the Coppa Italia with Inter Milan
Mancini's first job was at Fiorentina, a club in financial meltdown and forced to jettison their best players. Mancini worked unpaid on occasions and battled relegation but he won the Coppa Italia in 2001, beating Parma 2-1 on aggregate with goals by Paolo Vanoli and Nuno Gomes. More impoverishment followed with his next job at Lazio, where some players were required to take 80 per cent pay cuts and others, including Hernan Crespo and Alessandro Nesta, were sold.
Nevertheless, Mancini won the Coppa Italia in 2004, beating Juventus 4-2 on aggregate (Stefano Fiore scored three). This victory, coupled with impressive league finishes, caught the eye of Inter Milan.
Mancini followed the established patternthere, too. His first success was winning the Coppa Italia in 2005 (3-0on aggregate against Roma) and he retained it in 2006 (4-2 against Roma) before being handed the league title by default from a third-placed finish after Juventus and AC Milan were punished over the Calciopoli scandal.
The following year, however, Inter won the league outright, including a recordbreaking run of 17 consecutive victories. Mancini created a winning team by never forgetting the importance of cup success from his time at Sampdoria.
That is his blueprint for Manchester City, too. Some may sniff that the enormous investment of Sheik Mansour has yet to produce the coveted league title - and may only secure fourth place and the right to pre-qualify for next season's Champions League, unless Arsenal can be caught - but Mancini knows even the biggest plans take time.
Jose Mourinho won the League in his first season with Chelsea, but the club had been on the fringes of the elite for many seasons, had won the FA Cup and the European Cup-winners' Cup and had already been boosted by a year of funds from Roman Abramovich.
Up for the Cup: Mancini celebrates on Saturday
By comparison, City are out of nowhere, from close on four barren decades, with a rump of Champions League clubs who are more established than ever.
Abramovich did not have to compete with Russian oligarchs when he arrived in English football; he was the first. City must overcome the brilliant tyranny of Manchester United under Sir Alex Ferguson, the fabulous wealth of Chelsea and also have to displace Arsenal, who have been a fixture in the Champions League since 1998.
The other half of Manchester will crow that on Saturday they won the big one and, viewed dispassionately, that is most certainly true. City would swap this thoroughly deserved FA Cup win for the league title, and a place in the Champions League final, in a heartbeat.
What is inarguable, however, is that City have more chance of achieving either of those ambitions this morning than they had one week ago. Mancini has now established the idea of his team as winners.
Indeed, even the losers on Saturday, Stoke City, were in some small way winners, too, being propelled into European competition next season by Manchester City's qualification for the Champions League. While bemoaning the fact that his team did not turn up with the expected combativeness, manager Tony Pulis acknowledged what reaching the FA Cup final has done for his club. He sees it as a gift that keeps giving.
Early success: Mancini won the Coppa Italia in 2001 in his first coaching job - with Fiorentina
'We've played so well for the last 10 games and we very much benefited from the FA Cup this year,' he said. 'When we beat West Ham in the quarter-final that really took us forward and, before today, we had lost only one game since that match [away at Tottenham Hotspur, 3-2]. It just shows how important an FA Cup run can be.
'Staying in the Premier League was our priority but in Cup football the top teams no longer play their best sides so there is always a chance if you set yourself for it. This is our fourth year with Premier League status, we have been in two quarter-finals and a final in three years and we're going to embrace the Europa League next year. It will be wonderful for this club, for Stoke City, to say ''we're in Europe''. We've got Wigan Athletic in the last game of the season and it is sold out already.'
That, on a far grander scale, is what Mancini is looking to extract from his FA Cup final appearance, too. He believes his club lost their chance to compete for the league title with too many dropped points in February and March and wishes to increase the squad numbers, recruiting players with Champions League experience.
This will be stage two of his project, though. Stage one is complete. If Platt remains a tipster to his friends, there will be some Manchester bookmakers who are considerably poorer now than they were on Saturday morning.
?Matt Lawton: Mancini urges Man City owners to fund an assault on the titleManchester City 1 Stoke 0: Yaya the hero again as Blues end 35-year wait for trophyThink about what you'd be missing, Carlos! City chief urges Tevez to stayAll the latest Man City news, features and opinion
?Explore more:People: Tony Pulis, David Platt, Martin Samuel, Roman Abramovich, Roberto Mancini, Jose Mourinho Places: Manchester, Europe
Source: Daily Mail
Source: Daily Mail