A forthcoming Netflix documentary series on Jose Mourinho's career has confirmed what had long been rumoured: Manchester United believed they had secured Mourinho as Sir Alex Ferguson's successor in 2013 — only for the deal to collapse within days.

Sources connected to United describe the episode in the same terms: "sliding doors." The meetings had been going on for weeks, held in Madrid and London, with Ferguson personally telling Mourinho — a manager he held in high regard — that he intended to retire at the end of the 2012-13 season. Negotiations moved quickly to terms, and an agreement was reached.

Then it fell apart.

Mourinho's change of heart

Ferguson recalled the moment Mourinho reversed course: "One night, he phoned me and he was crying and he says: 'Alex, I can't take it. I've given my word to Chelsea and I'm not going to break my word.'"

Mourinho cited family reasons for walking away. Several figures inside United remain unconvinced that was the full story. It is true that Mourinho owns a family home in London and had pledged to return there after his first Chelsea dismissal in 2007. His positive relationship with former Chelsea owner Roman Abramovich is also thought to have been a factor.

A turning point in United's history

Those at the club considered the failed Mourinho approach a defining moment. Ferguson was leaving alongside long-serving chief executive David Gill, and the feeling inside Old Trafford was that Mourinho had the stature and temperament to manage a complex transition — not just a change of manager, but a restructuring of how the club operated.

With Mourinho unavailable and Pep Guardiola already committed to Bayern Munich, United turned to David Moyes. The Everton manager shared several of Ferguson's qualities but had not operated at the highest level of European football. United unveiled Moyes as "The Chosen One." He lasted less than a season.

What might have been

Sources who spoke for the documentary believe Mourinho's presence in 2013 would have made a material difference. Unlike Moyes, who hesitated in the transfer market, Mourinho was expected to act decisively. A move for Thiago Alcantara from Barcelona, sources stress, would have been completed. The costly, last-minute signing of Marouane Fellaini from Everton for £27.5 million — struck only after United missed a lower release-fee window — simply would not have happened.

Mourinho had already shared detailed opinions on a number of players he would have inherited, including Italy midfielder Daniele de Rossi. The general feeling is that he would have extracted more from Ferguson's experienced title-winning squad than Moyes did — a group that, under Ferguson in 2012-13, had already significantly overperformed before tumbling to seventh the following year.

When Mourinho eventually arrived

Mourinho did join United in 2016, replacing Louis van Gaal, who was sacked 48 hours after guiding the club to FA Cup glory over Crystal Palace. By then, the squad had changed considerably. Of the 18 players who had started 10 or more Premier League games in the 2012-13 title-winning campaign, only six — David de Gea, Phil Jones, Wayne Rooney, Chris Smalling, Michael Carrick, and Antonio Valencia — featured as heavily in Mourinho's first season.

Mourinho himself had also changed. His second spell at Stamford Bridge had ended in December 2015 with Chelsea 16th in the table, one point above the relegation zone. His time at Old Trafford brought the UEFA Europa League and EFL Cup in his first season, along with two UEFA Champions League qualifications. He has called finishing second in the Premier League — 19 points behind champions Manchester City — one of the finest achievements of his career. United's 81 points that season remain their highest total in any post-Ferguson Premier League campaign.

Yet he fell out with key players, including record signing Paul Pogba, and publicly accused the club's hierarchy of refusing to back him over striker Anthony Martial, whom he wanted to sell. The sense within the game is that an earlier arrival would have given Mourinho a greater impact — and United a smoother path forward. As Ferguson himself put it in the documentary, the phone call in which Mourinho tearfully pulled out was a huge blow. Arguably, United are still feeling it.