Heading into UFC 189, Conor McGregor's father assured those closest to him that his son held all of the aces. While the last-second opponent switch from Jose Aldo to Chad Mendes had been far from ideal, McGregor was the one who had a full training camp, and McGregor was the one who looked nigh unstoppable for four years and counting.

But then the music faded, Sinead O'Connor descended back into the bowels of the MGM Grand Garden Arena, and the Mendes takedown train starting roaring. One after another they came, planting the fighting pride of Ireland on his back for the first time ever in the UFC. And suddenly with each hard elbow that blasted their boy in the jaw, the McGregor contingent couldn't help the feeling of those aces slipping from their hands.

"I must say I was quite worried," McGregor's father, Tony, admitted Monday on The MMA Hour. "I went into shock when I saw him getting tossed around the Octagon by Chad. We didn't expect that at all. It was completely new to us and it was completely new to the fans as well. I was speaking to the fans after and they told me that they cried during that.

"I went into shock. My wife Margaret, she panicked and fled the arena, she ran into the back. Her two sisters were huddled into each other hysterical, and (Conor's girlfriend) Dee (Devlin), I think Dee was rooted to the spot crying as well, and this was all in the first round."

We know now, of course, that any of Conor's early danger was simply a preamble to his latest masterpiece. "The Notorious" answered Mendes' assault with a steady procession of body kicks plus a few grins, then finished his wearied opponent with a salvo of punches late in the second round, capturing Conor the UFC's interim featherweight title.

The moment was the culmination of a two-year rise like few we've ever witnessed in the UFC, one personified by equal parts bravado, perseverance and prediction -- and looking back, even Tony couldn't have foreseen such greatness from his young son.

"He had a determination about him, but the remarkable thing about it is, he was unremarkable, if you know what I mean," Tony said of his son's childhood. "That's the remarkable thing about it. He was a normal kid. He was going to school in junior high school. He would just come home, do his homework, team up with his buddies after homework and kick a ball about."

It's an improbable story, the path from unmotivated apprentice plumber to UFC superstar. And Tony certainly wasn't sold at first.

When his son first announced that he was quitting his plumbing career to instead focus on professional cagefighting, Tony fought hard to change his mind. Conor likes to say the two ultimately came to blows over it, and while Tony denies that claim, he does acknowledge that it took him much longer to come around than Conor's mother.

But eventually he did come around, and one moment early in his son's career confirmed beyond any shadow of a doubt that he had made the right decision.

"You must remember, he was only a boy to me at the time," Tony reflected. "I remember he was fighting some guy and his opponent dropped out for some reason or another, and on the night there was this big eastern European guy put in his place. So when they announced him, the eastern European guy came out to the lights and the music, and I just saw this guy. ‘Oh my goodness, this is some opponent.' I couldn't see Conor going through this guy.

"Conor just dispatched him in minutes in the ring. So I knew. That was the defining moment. If there was ever a defining moment, that was it for me. Incidentally it was also the moment in my eyes when he became a man.

"From then on, I knew. I actually knew then, he had a million dollar left hook. And I used to say that when I was driving around my taxi (at work). Conor was unheard of at the time, he was unknown outside of the immediate MMA circle. And I used to say, if I met a nice guy bringing them home in the taxi and they had an interest in sport, I used to tell them to about my son -- to remember the name Conor McGregor, he has a million dollar left hook."

Tony became one of Conor's most ardent supporters from that point on, backing his son's career choices even as Conor was struggling on welfare, fighting for a look from the UFC.

There were ups and down along the way, as there are with any future champion. But no mattered how many times he imagined it, no moment prepared Tony for the final climatic minutes of UFC 189, when UFC President Dana White wrapped a golden belt around his son's waist, and Conor's emotional family broke down into tears behind him -- the culmination of an agreement that was brokered long before, when Conor was teetering on the verge of quitting the sport.

"It a deal that went back maybe six or seven years ago," Tony said. "It was a deal between John (Kavanagh) and Margaret that when he wins the UFC championship, that Margaret will be in the ring when he's accepting the belt. So that pledge was honored on the 11th of July this year. It was really an amazing, very poignant moment for the whole family.

"It's great to see a young man who can defy convention and defy his family and come through in such a short time to realize his dream," Tony added. "It's an amazing story, and we're immensely proud."