Hindsight is a beautiful thing in football, but it really does seem mad that the Manchester United hierarchy allowed Nemanja Vidic, Rio Ferdinand and Patrice Evra to all depart the club in one summer.
Vidic, of course, decided to move on way before the transfer window as he announced he was leaving the club for Italian outfit Inter Milan in early March. Ferdinand and Evra, meanwhile, left a few months later for QPR and Juventus.
This season, without the trio of experienced stars, Manchester United have endured a nightmare opening period. In attack - with the likes of Angel di Maria, Radamel Falcao, Wayne Rooney and Co. at Louis van Gaal's disposal - United are a force to be reckoned with.
In defence, however, they look vulnerable and short of confidence. Youngster Tyler Blackett - who was sent-off in United's nightmare at the King Power Stadium this past weekend - has been thrown into the side despite struggling to make an impression at Championship outfit Blackpool last term.
Then comes the likes of Jonny Evans and Chris Smalling who have also failed to prove their credentials so far. Mistakes have been made, but these players have struggled to learn from their costly errors.
In fairness, Phil Jones has impressed for the Red Devils under the new regime. After all, the England international was handed the club's Player of the Month award for August. Injury, though, has once again taken its toll on the 22-year-old, but United fans will be desperate to see him return sooner rather later.
But what United's back-line really needs is a defender full of experience who represents a leader on the pitch.
Manchester United are crying out for a natural leader who has been there and done it before. Vidic has, without a doubt, proved his class at Old Trafford over many years, and still has life in him.
As he returned to fitness last season, why on earth did Ed Woodward and David Moyes fail to offer him one last deal at the club? It was clear that Rio Ferdinand - at 35 years-old - was on his way out at the end of the season, so keeping Vidic should have been a priority.
Losing Vidic and Ferdinand in one go took away the spine at Old Trafford - and it hasn't been replaced. Of course, Moyes may well have looked to replace the defensive duo if he had stayed in charge at the Theatre of Dreams, so Van Gaal must take part of the blame for failing to sign a world-class replacement.
But, in fairness to Van Gaal there aren't many top defenders available on the market right now. Moyes should have recognised that too as he planned for the future. Perhaps, then, Moyes' inability to keep Vidic has harmed Manchester United's chances of success.
He would have helped
It's not just at centre-back where United have struggled. Rafael da Silva, Antonio Valencia, Marcos Rojo and Ashley Young - who have all featured in the full-back or wing-back role this season - have all looked out of place and struggled to adapt under the new regime.
Vidic, then, could have led these new stars and calmed everything down. At Leicester this past weekend, United fell apart. Wayne Rooney - the leader of the team on the pitch - tried to fire up his teammates, but was unable to really get them going. And, in truth, it's never going to be an easy task for any striker to lead a back-line.
It's not just Vidic's leadership and experience that Manchester United miss. At 32-years-old, Vidic could still walk into this team. He's a dominant figure and striker's wouldn't feel at ease in and around his presence.
Forget Vidic's age, there's no way the Serbian would have let Leicester's Jamie Vardy bully him on Sunday. There's a reason why the Stretford end at Old Trafford had a special song for the powerful centre-half. He was never afraid to get involved and would have done anything for the team and for the three points.
Of course, many will suggest that his heart was set on a move away from Old Trafford, but the United hierarchy should have done more to try and keep him. A contract wasn't offered, so he had to look elsewhere.
Terry proving his worth
You only have to look at league leaders Chelsea to see how an influential defender can continue to star at the highest level. John Terry - despite being older than Vidic - is still going strong at Stamford Bridge.
He made light work of Sergio Aguero, Eden Dzeko and Co. at the Etihad, proving he still has everything to offer. Chelsea are a solid team, and Terry is still crucial to their success.
Just after United shipped five goals against one of the Premier League new-boys, Chelsea's back-line - led by Terry - kept one of the best attacks in world football at bay.
Vidic, meanwhile, may have struggled in his opening games at Inter - he's been sent off, given away a penalty and made a costly error in his opening couple of games - but he's still an upgrade on Manchester United's current defensive heart.
Give him another couple of games in Serie A and he may well return to his best form. If only he was still playing in red.
Manchester United fans: Should the club have done more to keep Vidic? Have your say in the comments section below!