Alexis Sanchez will play in his first Champions League game for Manchester United on Wednesday when they take on Sevilla in the first leg of the round of 16.
The Chilean's last appearance in the competition was when he came on as a second half substitute in Arsenal's humiliating 5-1 defeat to Bayern Munich, which took the aggregate score to 10-2.
Before those games, Sanchez had reportedly been open to extending his contract with Arsenal, but the manner of the defeat sparked him in to action. He knew he had to find a new club.
At United, he is playing for a manager who has won the Champions League twice for two different clubs. Neither Porto or Inter Milan were considered anything like favourites at the beginning of those campaigns but Mourinho was able to get every ounce of fight out of his players to claim the trophy.
The manner in which Inter knocked out Pep Guardiola's Barcelona, the team that won La Liga with an astonishing 99 points that season, was typical Mourinho. His team went down to 10 men at Camp Nou after 27 minutes when Thiago Motta was sent off. It wasn't until five minutes from time before Barcelona were able to break the deadlock, yet Inter clung on to the narrow 1-0 defeat which saw them go through to the final 4-2 on aggregate.
"We were a team of heroes, we sweated blood," Mourinho said at the final whistle, hailing the incredible shift his 10 players put in to knock out one of the greatest club sides of all time.
There's no denying that Mourinho's behaviour is atrocious at times and it would be disingenuous to dismiss this as purely a by-product of the passion he has for the game or his strong desire to be victorious, but there's no getting past Mourinho's unyielding desperation to be a winner.
That urgency is fed to his players and, although he struggles to maintain that battling nature for long periods of time, this creates winners out of every team he manages.
"He's the leader of his army," Zlatan Ibrahimovic reflected in his autobiography in 2013. "Mourinho would become a guy I was basically willing to die for."
It is this mentality that will suit Sanchez more than Arsene Wenger's approach ever could.
Hector Bellerin was asked about his former teammate this week and he claimed that Sanchez "always wants to win" and that "he demands from everyone, and sometimes it can be quite too much." If you didn't know otherwise, this could be someone describing Mourinho.
Henrikh Mkhitaryan said as much when he swapped United for Arsenal (with Sanchez going the other way) in the January transfer window.
"Mourinho required a lot from the players. A lot, he was very hard," he said after the move. "Arsene Wenger is friendlier, he understands, can think about players' situations, is calmer. That's the difference."
Mkhitaryan struggled to perform consistently at United, showing flashes of brilliance but too often crumbling under the pressure of the big games. Sometimes you wouldn't even know he was on the pitch as he faded into the background and seemed incapable of stepping up to the plate when it was required of him. His preference for Wenger, a manager who doesn't put the same weight of expectation on his players (which has resulted in never winning the Champions League and going 14 years without a Premier League title), tells us something about Mkhitaryan's mentality.
If Bellerin's descriptions of Sanchez are true, then Wenger was never going to be the right manager for him, while Mourinho's qualities are perfect.
Patrick Vieira is one of the few players to have played for both managers but despite making his name under Wenger it was Mourinho at Inter who impressed him the most, when asked to compare the two.
"He's the manager who had more influence on me," he said. "Why? Because he was the one who impressed me most on his work ethic. He always got the best out of his players."
Claims that United can win the Champions League this season will be scoffed at, and rightly so given how far behind Manchester City in the league they are. Bayern Munich and Barcelona are also running away with their leagues too and not even the most biased United fan could suggest the team is close to the level of Europe's best at the moment.
But Mourinho doesn't need to have the best 11 players to win the Champions League; he just needs those who are as hungry for victory as he is, as he showed in 2004 and 2010.
This United squad haven't done enough to suggest that they are where Mourinho needs to be crowned champions of Europe, but in acquiring Sanchez they've added a player who is driven to succeed and could make the difference.
It would be an uphill battle if United are to lift the trophy but stranger things have happened and Mourinho has been responsible for some of them.