End up on the wrong side of Jose Mourinho at your own peril. Luke Shaw has found that out the hard way, even years after the two parted ways at Manchester United.
It may be fair to argue that the left back's career has enjoyed a steady rise, while Mourinho's stock plummeted somehow at his sacking at Tottenham. Now in charge of Roma, there will be plenty to occupy his mind.
Bizarrely, though, it appears he just can't lay his bizarre frosty relationship with the player to rest. Every now and then he will unleash his latest barbed comment, all while a rejuvenated Shaw continues to impress.
The most recent swipe came when Mourinho took aim at Shaw's corners during England's win against Czech Republic, and even that came just days after he insisted he would have moved Ben Chilwell ahead in the pecking order.
This is a feud that stretches across almost four years, from Mourinho's early days at Old Trafford to now. The comments have often been scathing, leaving Shaw to try and wave them away by pointing out his newfound contentedness.
So, how did it all begin? Cast your mind back to 2015, and Shaw's horror double leg break. Aged just 21, the Three Lions defender was left sprawled out on the turf after a crunching tackle from Hector Moreno.
A glance down showed the gruesome extent of the injury. He was told in hospital six months on that the shattered limb was at real risk of amputation, and his recovery was a difficult road marked with anguish.
Both physically and mentally, Shaw set about trying to repair himself. When he did return, Louis van Gaal was no longer the manager, with Mourinho replacing him.
After a number of other setbacks, Shaw finally was ready for first-team action, but then came the infamous fallout after 1-1 draw against Everton. Along the touchline, Mourinho was seen prowling, seemingly instructing the player at every turn.
After the game, the coach turned his attentions to Shaw, and set about tearing apart almost every aspect of his middling performance.
'He [Shaw] was in front of me and I was making every decision for him,' Mourinho said, the press taking in every word.
'He has to change his football brain. We need his fantastic physical and technical qualities, but he cannot continue to play with my brain.'
Shaw was also instructed to 'grow up, mature and understand the game better'. The approach towards motivating, or otherwise, the United man was one rarely seen in the full glare of the cameras under Sir Alex Ferguson.
To no surprise whatsoever, their relationship was never fully patched up. The distance between them was evident, and Shaw was understandably left crestfallen about what the future may hold.
'I cannot compare the way he trains [with team-mates], the way he commits, the focus, the ambition. He is a long way behind,' Mourinho said in 2017.
'It is about seeing everyone as individuals and human beings,' he added. 'I did spend a lot of time speaking to individuals and Luke as well. He is a boy I enjoy talking to, I enjoy trying to help him. He wants to be better.
'It was about getting him to enjoy his football. We know his talent, but it was trusting his fitness, injury-wise, having players who can back him up.'
The carrot and the stick approach is rarely effective when the victim is being struck over the head with ruthless ferocity, and Shaw was sent into a tailspin. It wasn't until Ole Gunnar Solskjaer steadied the ship that his clear talent resurfaced.
Mourinho, of course, had his reasons. He had every right to feel aggrieved with many of them. His frustration was directed at occasional tardiness, fitness issues and an irksome knack for making the wrong decisions on the pitch.
The Manchester Evening News recall a particular moment during United's pre-season tour in Perth in 2019, long after Mourinho was ousted, when Shaw was outrun - and even lapped - by a fitness coach.
This jaw-dropping moment was viewed by some as proof that the Portuguese's methods were justified, and that Shaw's professionalism simply dipped under the necessary standards needed to succeed at the club.
There was also an occasion during Mourinho's stewardship where Shaw reported to Carrington, United's training base, late. When an explanation was demanded, the full back explained his mother had overslept and forgot to wake him.
Mistakes were made, but not forgiven. In the end, though, it was the player who outlasted the manager.
After making just 19 appearances in both of his two full seasons under Mourinho, from 2016 to 2018, Shaw was handed a refreshing new slate. Mourinho was too. But even now, both have reminded the world of their rocky past.
'I always believed that I would be able to do it,' Shaw told the Manchester Evening News, when questioned about fighting through the criticism.
'There were maybe people who were saying, when I was going through the bad times when I wasn't playing, people were telling me to get out of there and go and play somewhere else.
'No one wants to leave the biggest club in the world and I believe there was a reason why I was brought here and I didn't want to leave and not show what I can do. I dug in deep, I didn't let anyone affect me.'
Mourinho tells a different tale altogether. His recollection is one centred around trying to eek out the very best from Shaw, and help him develop his maturity both on and off the field.
'I found a boy after an incredible injury which risked his career,' he told talkSPORT.
'I found a boy with some fear and emotional scars. I was trying to improve mentalities, I was trying to make ambition and responsibility - to grow up.
'It was not easy for him and I have to admit that I pushed the players to their limits, and sometimes players are not ready to follow me.
'We had a good period. He has a lot of talent.'
As with any disagreement, there are two sides, two different stances.
It is perfectly clear that Shaw feels more comfortable in his own skin under the more affable Solskjaer, and his encouragement helped him to become arguably the Premier League's best left back last season.
He would have every right to harbour resentment, but when quizzed on the back and forth with Mourinho, Shaw is keen to stick to measured answers.
'It was a mixed relationship,' he has told SPORTbible.
'A lot of the things that happened between us two, sometimes he went about it in the right way. I think a lot of people will agree with that at the club.
'Our relationship wasn't the best. It was probably quite easy to see that from the outside. But one thing Jose did do was make me mentally much stronger. I think mental strength is what I would describe that period under Jose Mourinho.
'I think I felt part of the team under Ole, whereas under Jose sometimes I didn't. Ole showed his belief and confidence in me. I always believed good times were coming. I stuck in and dug deep; went through a lot but came out better on the other side.'
The end result was a fine campaign, which saw him make 47 appearances and score one goal, and a prominent role with England at Euro 2020. He plays with a smile on his face, and is brimming with confidence.
His current state of mind will be a far cry to Mourinho's days.
'What does Luke Shaw need to do to get on to the bench?' a reporter asked Mourinho in April 2017.
The response was made up of three letters, each dripping with the Mourinho vitriol countless players have had the misfortune of experiencing. 'Who?'
It didn't end there, either, with Mourinho also insisting: 'He is a long way behind.'
Well, he's not anymore. He is succeeding despite the criticism sent his way, and not because of it. Finally, the promise shown when he first arrived as a fresh-faced 18-year-old is there for all to see.
With each broken fitness record, inch-perfect cross or marauding dash down the touchline, his doubters are being proven wrong, and that includes Mourinho.