Just like every other Premier League club, Manchester United have made their fair share of transfer blunders down the years.
From signing Anderson for €30 million in 2007 to letting Paul Pogba join Juventus on a free in 2012, no doubt Sir Alex Ferguson has plenty of regrets.
One of the biggest mistakes Fergie made in an otherwise hugely successful 27 years at United, though, was sanctioning Gerard Pique's sale to Barcelona in 2008.
Barca only paid £5 million for the Spain international, who has since become one of the world's best centre-backs and won every major trophy at both club and international level.
Pique turns 31 years old today (February 2) and to celebrate, some interesting stories have re-emerged online about his time at the Theatre of Dreams.
Back in 2014, for example, Pique was asked in an interview with FourFourTwo magazine if he was ever on the receiving end of the Sir Alex's infamous 'hairdryer treatment'.
"The what? Oh right. Of course!" said Pique, who needed reminding of what the 'hairdryer treatment' was. "At the beginning I couldn't understand a word he (Fergie) said.
"I was just relying on his face or body language his accent was so broad. Mancunian is hard enough, but Scottish is impossible!"
Pique was also asked if the former United manager scared him, to which he said no but named a former teammate as someone he didn't like to cross: Roy Keane.
Keane was famed for being football's hard man during his playing days and there was one incident in United's dressing room where Pique almost came to blows with the Irishman.
When Pique's phone started ringing in his pocket in the dressing room, Keane could "hear the vibrations" and "went crazy" as he asked everyone who was responsible.
"I wouldn't say I was scared of [Sir Alex Ferguson]," added Pique. "[But] Roy Keane? Well, maybe that's different!
"I remember we were in the changing room at Old Trafford and my phone started vibrating. Keano could hear the vibrations and went crazy trying to find out who the phone belonged to. That's who he was.
"Before we (Barcelona) beat Celtic 1-0 last season, I noticed him by the side of the pitch as a pundit as we went to warm up. I hid my face with my hand because he still scares me. I was 26 years old, and I was sh***ing myself!"
That's the Keane effect for you - although Pique never revealed exactly what happened when the former United captain found out it was his phone ringing...