LONDON • Chelsea were leading Porto 2-0, having been in control for most of the game. Jose Mourinho decided to take off Eden Hazard, who had been involved in the build-up to both Chelsea goals.
It had probably been Hazard's best performance of the season to that point and he left the pitch to warm applause. He slapped hands with Loic Remy but then, as Mourinho went to congratulate him, Hazard shrugged him off.
That moment was emblematic of the disintegrating relationship that was at the heart of Chelsea's turbulent 2015/16 season, which led to Mourinho's second departure from the Blues.
As the Manchester United manager prepares to take on his old club today, he knows full well that the man he had once labelled "my new Messi" could very well come back to haunt him, putting the Red Devils further away from a top-four finish this season.
Five days after the Porto incident, when Leicester City and Claudio Ranieri put the final nail in the coffin of Mourinho's second Chelsea tenure, there came the strange incident of Hazard's hip.
Mourinho clearly felt Hazard, who had been troubled by the problem since the summer, was not particularly badly injured and cajoled him to go back on after treatment on the touchline, only for the Belgian to decide within seconds that he did not fancy it and march off, ignoring his manager as he did so.
- Premier League goals Eden Hazard has already scored this season, 10 more than he managed in the entirety of Chelsea's lacklustre title defence last season.
Not surprisingly, Hazard was one of three players highlighted as "rats" by disgruntled Chelsea fans the following weekend, but it was typical of the duo's frayed relationship, even though things went well at the start, when Mourinho rejoined Chelsea in 2014.
Even then, he would provoke Hazard in front of the squad, telling the team, "Today we're playing with 10", to try to goad him into greater defensive effort.
Initially, Hazard, used to more overtly supportive managers, was troubled. "If he looks you in the eye, it's terrifying," he said.
Hazard is not a natural rebel, however. He accepted his manager's ways, even if he preferred to go home and spend time with his family after training rather than staying for extra gym work.
The two found an understanding and, while there were occasional hiccups, the relationship worked. When Hazard was named Chelsea's Players' Player of the Year and joked that the other nominees would have to work harder, Mourinho appreciated the dig.
That was the height of their connection. Mourinho recognised Hazard as a humble, diligent player lacking a little ambition. He began to acknowledge his respect for Hazard, highlighting an opponent in team meetings and saying he was "no Maradona, no Messi, no Hazard".
The warmer approach brought the best out of Hazard and Chelsea won the Premier League as Hazard was named PFA and Football Writers' player of the season.
But then Mourinho ramped up the pressure, describing Hazard as "my new Messi" while at the same time urging him to take more defensive responsibility.
At the same time, Hazard was struggling to recover from a hip problem that afflicted him until last April. At one point, a frustrated Mourinho allegedly told him: "You're not good enough for the top. I'll have to sell you."
As reports surfaced that the pair had fallen out, they met to discuss the situation. Hazard asked to play centrally and Mourinho agreed for the home game against Liverpool.
With the score at 1-1, though, Mourinho took him off, shattering what remained of Hazard's confidence.
Yet there is no acrimony between the two. When Mourinho was sacked, Hazard sent him a text message saying he felt responsible because he had not been at the same level as before. Mourinho replied, accepting Hazard's sentiment and wishing: "Good luck to you and your wonderful family."
Mourinho felt he lacked the necessary hardness; by the end Hazard, along with a number of players, felt wearied by Mourinho's relentless abrasiveness. In Hazard was expressed a wider malaise.
Hazard has clearly benefited from taking a more central role this season. Playing almost as an inside-left in Antonio Conte's 3-4-2-1, he has been able to drift infield, knowing Marcos Alonso is always there to go outside him and offer creative width, while also being able to initiate the press, if required, on the opposing full-back.
For all the meticulousness of Conte's planning, that perhaps has made his movement less predictable and with that freedom within a system some of the swagger has returned to his play.
Hazard has taken full toll on Mourinho as well, scoring one and generally sparkling with menace in Chelsea's 4-0 win over Manchester United.
So dangerous was he that for the FA Cup quarter-final in March, Mourinho seemingly targeted Hazard.
Whatever the rights and wrongs of Ander Herrera's dismissal in that game, the red card resulted from Hazard being kicked every time the ball came near him, an intriguing focus, taking into account Chelsea's slickness as a unit this season.
Given the way that game went, any strategy to counter Hazard on Sunday will have to be rather more subtle.
And if United are to prevail, Hazard will have to be neutralised.
For Mourinho, perhaps, that is not only a tactical imperative but also a psychological one.