In terms of football management, one man stands head and shoulders above any other in terms of success with a single team.
Sir Alex Ferguson's leadership of Manchester United was the most devastating ever witnessed in the game, with the Red Devils claiming every title there is to win on multiple occasions.
Premier League, Champions Leagues, FA Cups and League Cups all fell into the hands of the legendary Scotsman, who seemed to be able to build a world class squad almost out of nothing.
But, this does not mean Ferguson was perfect as like most normal human beings, he was prone to the odd mistake.
Some of his errors came from the players he signed, with failure such as Kleberson, Eric Djemba-Djemba, Bebe and Anderson optimising his imperfect scouting network.
However, perhaps his biggest mistake comes from a player he missed out on back in 2011.
United were after a striker to partner Wayne Rooney as they clearly didn't see Danny Welbeck as a viable long-term solution.
A year later, they would sign Robin van Persie from Arsenal but the summer before that, Ferguson rejected the chance to sign none other than Sergio Aguero.
AGUERO COULD HAVE BEEN IN RED
United were in negotiations with Atletico Madrid but baulked at the £38m asking price. Their bitter rivals City duly swooped in and signed him, with the Argentine going on to become a Premier League legend in sky blue.
"His agent was demanding a price we were not prepared to pay," Ferguson wrote in his book, Leading, per Manchester Evening News.
Ouch, not the best but of business, particularly as £38m is not a bad price for a player that was as clearly as talented as Aguero was, even back then.
Put it this way, Andy Carroll had joined Liverpool in a £35m deal that January, £3m more for one of La Liga's finest was always going to be a good deal.
Still, United weren't too bothered in 2012/13, when Van Persie lead them to the title.
But, the Dutchman's time at United didn't last too long and Aguero is still going strong for City as we speak.
Hindsight is a beautiful thing and by using it, it's easy to say rejecting Aguero was the wrong decision.
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