The 3-4-2-1 formation used by Watford during the first half against Manchester City showed what Beppe Sannino could achieve in a short space of time.
After the match, Hornets midfielder Sean Murray confirmed the players had not tried the new system prior to Monday last week.
Now, the 3-4-2-1 formation may have been used by a few of us on FIFA computer games over the years but it isn't a system used on a regular basis by coaches. So the 3-4-2-1 wouldn't have been ingrained on the players growing up, like the 4-4-2 for English players and 3-5-2 for Italians may have been.
If Watford had dominated Manchester City for nearly all of the first half having worked on a formation for the whole season then it would have been an impressive feat. After all, Premier League managers - young and old - had tried and failed to stop the City juggernaut, with Arsene Wenger, Andre Villas Boas, Sam Allardyce and Chris Hughton all seeing their team ship at least six goals in the last few months.
City made a few changes at the weekend but 17 of the 18 players in their squad were full internationals and their strike pairing of Sergio Aguero and Edin Dzeko have now scored 41 goals between them so far this season.
So for Sannino to instil a system which would not only nullify City's threat but also open them up with relative ease in just five days of preparation is truly remarkable.
The praise should not be restricted to just the head coach either. Watford's players produced a monumental effort and seemingly implemented Sannino's instructions perfectly in the first half.
With City averaging four goals a game at the Etihad this season, you would understand if clubs attempted to 'park the bus' when they face Manuel Pellegrini's side. But the Hornets not only restricted the Sky Blues' threat, the decision to play Ikechi Anya and Fernando Forestieri off Troy Deeney meant the Golden Boys were always ready to counter-attack with numbers.
Every time a City attack broke down, the likes of Sean Murray and Cristian Battocchio had a forward pass available and the Premier League title favourites could not cope. Watford had two glorious openings even before Forestieri scored the game's first goal midway through the first half.
City were pushing their full backs Micah Richards and Aleksandar Kolarov high up the pitch but that was playing into the Golden Boys' hands as they often found themselves three-on-three - or better.
Joleon Lescott and Jack Rodwell had a rare chance to impress for City as they look to secure World Cup places this summer but the pair - along with their team-mates - couldn't cope with the pace and movement of Watford's play.
The visitors deserved to lead 2-0 at half time and the fact Pellegrini sent for captain Vincent Kompany and the reliable Pablo Zabaleta at the break gave a clear indication of the Hornets' performance.
City took control at the break. After Aguero had pulled a goal back on the hour mark, Sannino tried to stop the onslaught by taking off Forestieri and bringing on Marco Cassetti, as he shifted to a 5-4-1 formation.
This dampened City's attacking threat slightly but it also reduced Watford's counter-attacking possibility significantly, as Deeney was left to plough a lone furrow, working off scraps.
An equaliser, which came in the 78th minute, seemed inevitable but the 4-2 scoreline slightly masks the fact the visitors were less than five minutes from forcing one of the biggest - and richest - clubs in Europe to a lucrative replay.
It was an afternoon which Sannino, the players and the 3,352 Watford supporters will never forget.
For around an hour, the magic of the FA Cup was alive. It was an afternoon which made you reminisce about spending all day watching the FA Cup final coverage as a child. It reignited the emotions which made you fall in love with the beautiful game as a kid. Of playing football all afternoon in the summer.
The key for Watford now is to use the performance as a catalyst for the rest of the season; to kick-start their play-off challenge.
It will be intriguing to see whether, with Nottingham Forest unbeaten since November and sitting fifth in the table, Sannino decides to give the 3-4-2-1 formation another go. If he doesn't, he has another three days to work on a plan.