Allowing Mark Hudson to leave Cardiff City in the manner he did is the worst thing Ole Gunnar Solskjaer has done to someone in football, according to the Manchester United manager.
Hudson was a bona fide fan favourite in the Welsh capital and is still remembered fondly by Bluebirds fans for what he did for the club during his stint.
During his five years with the club, he donned the captain's armband and helped seal City's first promotion to the Premier League.
However, following relegation from the top flight, then Cardiff boss Solskjaer had sought to bolster his defensive options, recruiting Sean Morrison from Reading, with a deal for Bruno Manga seemingly in the works, too.
Hudson knew that would see his game time reduced, but when he confronted the manager he claims he was assured that would not be the case. But, just a day before the summer window closed, Solskjaer told him he could leave, affording Hudson no time at all to find a new club.
Fortunately, Huddersfield Town came in for him and, under David Wagner, Hudson and the Terriers earned promotion to the Premier League.
And it was during one Premier League fixture between Manchester United and Huddersfield Town in which Solskjaer sought to apologise to the former City captain.
"We played Man United and we were winning at half-time," Hudson said on the most recent episode of the Undr the Cosh podcast, hosted by ex-Bluebirds forward Jon Parkin.
"Ole, the Man United manager, came to our bench and I was sat behind the bench, helping out with analysis at the time. He walked across and he grabbed me to say 'can I have a quick word?'
"So we were in the tunnel and he apologised. He said 'that's the worst thing I've done to someone in football. I felt stressed at the time and I made a mistake. I'm buzzing you are doing well and you've had the career you've had and you're in the Premier League and every bit of praise you've had'.
"And I thought, 'do you know what? That is unbelievable'.
"To be fair, he pulled me again after the game. He got someone to find me - and they had just lost, by the way, 2-1 at Huddersfield.
"And he is waiting off the bus, their coach, making them wait, to speak to me and to say it again, 'I really apologise for what went on'."
During the podcast, Hudson spoke candidly about the major trauma he and his family suffered during his first year with the Bluebirds.
His wife's sister took her own life on the day he signed for Cardiff City back in 2009 and weeks later his then-pregnant wife Marie-Louise lost their baby, which he touched on during his interview with WalesOnline last year.
He also discusses the kit change, pre-season tours under Dave Jones and the wealth of talent Cardiff boasted around that time.
Most notably, he speaks of the impact Craig Bellamy had on the club and the standards he demanded behind the scenes.
Bellamy, who was on loan from Manchester City at the time, was ruthless on the training ground, Hudson recalled.
"He was harsh," Hudson said. "In training, as soon as he got on to the grass, he took things so seriously.
"I remember Quinny [Paul Quinn] once shouting 'boom!' when someone just scored a top goal, top corner, in seven-a-side.
"Bellers stopped the session and just said, 'what? what did you say?'
"His eyes, wow, he could cut you. 'That's not what we are here to do! We are here to train and win'."
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It was during Bellamy's loan period with Cardiff City that then Wales manager Gary Speed tragically took his own life.
Bellamy and Speed were incredibly close friends and it clearly hit him hard. So much so, in fact, that he was considering hanging up his boots forever.
It took a tough phone call from Hudson to bring Bellamy back from the brink of premature retirement, an intervention which the former Liverpool forward truly appreciated.
"Obviously, it hurt Bellers a lot," Hudson said of Speed's death. "He was away from the club for quite a while, two or three weeks, and I caught wind that he was maybe thinking about jacking football in.
"Everything I had been through, we had been through as a family, I knew he was hurting. I thought I would call him and see if he needs anything or someone to talk to, because it hits people so hard.
"I just phoned him and said, 'look, I've been through it. I've been through something so sad and abrupt and disruptive to your life. But Speedy wouldn't want you to jack football in. He would want you to play and do what you love doing. Come back and see how you feel'.
"He did, he came back, two games in and he scored. Bellers isn't outwardly emotional, but he celebrated with everyone and as we were running back, he put his arm around me and said, 'if it wasn't for you, I wouldn't have come back. So thank you very much'.
"And he is not like that. But, after he scored, to say that to me, I was running back and I nearly teared up."