Jose Mourinho declined the opportunity to manage Manchester United after Sir Alex Ferguson's retirement, a choice that has had a lasting impact on the club, according to sources. The Portuguese manager expressed his decision to Ferguson himself, citing reasons that led him to ultimately say 'no' to the prestigious role.

Mourinho's potential tenure is believed to have been a sliding door moment for Manchester United. Had he accepted, his proactive approach to transfers might have prevented key missteps. Unlike the subsequent management, Mourinho is thought to have been decisive in the transfer market. For instance, a move for Thiago Alcântara from Barcelona was reportedly agreed upon and would have been finalized had he taken the helm.

Furthermore, the club might have avoided the problematic acquisition of Marouane Fellaini. The Belgian midfielder joined on deadline day for £27.5 million, a move that occurred only after United missed an earlier, lower release clause opportunity. Sources suggest Fellaini simply would not have been signed under Mourinho's directorship.

Mourinho had also provided input on potential player acquisitions to Manchester United, even suggesting Italy midfielder Daniele De Rossi. Beyond signing new talent, it is felt that Mourinho would have been able to extract more from the experienced players already in the squad he would have inherited.

While it is widely acknowledged that no one could have achieved more with Ferguson's final title-winning team than the Scot himself, and that squad significantly overperformed, the subsequent dramatic drop in performance to seventh place was unexpected. Players themselves have reportedly struggled to pinpoint specific reasons for the decline, but the prevailing sentiment is that Mourinho's presence would have provided the necessary impetus.

The impact of Mourinho's decision was significant, with Ferguson recounting the manager's emotional explanation for not taking the job in a documentary. The feeling within football circles is that Manchester United has not fully recovered from missing out on their preferred candidate to replace Ferguson.