Like every manager, Jose Mourinho is ambitious. He loves a challenge—a project where he can achieve something great and look back with nostalgia when he retires.
When he took over at Porto in 2002, not one person expected him to lead the Portuguese giants to the Champions League trophy in 2004.
But he did.
And, when he was appointed by Roman Abramovich as Chelsea manager, few predicted he would lead the Blues to back-to-back Premier League titles.
Oh, but he did.
Even when he decided to take charge of Inter Milan, there were doubts over Massimo Moratti's decision to hand him the manager's job. Two years after arriving, he delivered an unprecedented Treble in Italy.
A man who is so obsessed with success would surely jump at the chance to manage Manchester United. So when he was presented with the opportunity to pursue the Manchester United job, why did the 50-year-old refuse to even contemplate taking over at Old Trafford?
The former Real Madrid manager, who ended his three-year association with the club in May, signed a four-year contract at Stamford Bridge after being approached for a second spell at the club.
He was, however, linked with taking over at rival Manchester United following Sir Alex Ferguson's retirement, per The Mirror. The pair have become friends after several encounters, and Mourinho was full of admiration when his side progressed at the expense of Ferguson's Manchester United side.
Despite their mutual respect for another and the Portuguese tactician's incredible achievements in his managerial career, the Lancashire-based club opted to bring in David Moyes to revel in the spirit of long-termism.
Perhaps it's a similar situation to when a player leaves a club which meant a lot to him and later on in his career is presented with a tempting opportunity to join one of their rivals.
The fact that Mourinho still had a strong bond with some of Chelsea's senior players, such as John Terry, Petr Cech and Frank Lampard, would have played a part in his mind.
To line up against them as Inter Milan's coach was difficult enough, but to do it at least twice a season would be emotionally damaging for both parties.
Then again, is it really the same with managers? Rafa Benitez certainly displayed his lack of empathy towards former club Liverpool when he decided to take over at Chelsea four years after departing from Anfield.
The Treble-winning coach was asked by reporters during his first interview as Chelsea manager about whether he was hurt at not being offered the job. He simply smiled and replied: "I am where I want to be."
The smugness behind the smile suggested that he would not have been interested in taking the reins at Manchester United, per ESPN, even if he was offered the role.
Quizzed about the issue again only a week later, he insisted that he would have "turned down every job in the world - the Manchester United job, everyone - for Chelsea", per BBC Sport.
The key factor is that it's almost destiny that has brought Mourinho and Chelsea back together after a six-year break.
Of course, "The Special One" experienced overwhelming success in 2011-12, with Real Madrid winning La Liga by securing 100 points, while Chelsea triumphed in the Champions League final against all odds.
Yet, the 2012-13 campaign was a complete and utter shamble. Up until last season, Mourinho had never completed a campaign without winning a trophy in his 11-year career. And even despite missing out on defending their La Liga crown, the Copa del Rey final offered him a lifeline.
A 2-1 defeat followed at the hands of their fierce rivals Atletico Madrid—their first loss to the Rojiblancos since 1999—in their own stadium was humiliating, and it was a disappointing way for him to bow out of Spanish football.
As a wounded figure keen to put things right, going straight into a job as pressurizing as Manchester United would be too much of a risk for the 50-year-old. Putting his reputation as the world's best manager on the line for a job is an unnecessary gamble.
When he won the Treble with Inter, he announced that he was leaving the club. Why? Because he had reached the peak of his tenure at the San Siro.
He knew that his achievements could not be topped by anyone and leaving on the highest of highs made certain his time would be viewed as nothing other than a resounding success. It's also worth noting that his successor, Rafa Benitez, experienced an unspectacular, short-lived stint with the Nerazzurri.
And combining that point with Ferguson's 26-year reign coming to an end, you can understand why Mourinho may believe it would be impossible to replicate what the Scot achieved. It's not inconceivable to think that, as a friend of Ferguson, it would not be right for him to try to emulate that success.
On the other hand, he has the chance to be a hero with Chelsea once more. To save them from sliding into the clutches of mediocrity would be another notch in his wonderful career to date, and as we all know, Jose Mourinho loves to be the hero.
As the respective parties enter a new period in recent history, it's not too long before Jose Mourinho and Manchester United meet again.
Only then will they begin to wonder what might have been.