It was a huge blow to his confidence, but looking back, O’Nien says it was a watershed point in his career that he utilized to fuel him.

“I had some untapped anger in there, the anger was I felt like I got put out in the debut with my hands a bit tied together,” he told O’Nien on the Paul Mort Talks Sh*t podcast.

“We were man for man at Wycombe.” As a result, when I joined Sunderland, my entire league education was centered on man for man. Sunderland do not play man for man since they are a football team. When you’re on a ball-playing team, you have to find space, so when I walked onto the pitch, everyone (teammates) was like, “What are you doing?” we are not man for man here’. I lost it (the ball) a couple of times and I could hear the groans.

“Now, I haven’t got the skill-set to play in front of 35,000 people because I haven’t learned it yet. So then, the manager (Jack Ross) at half-time said ‘we are taking you off, it’s a tactical change’.

“I sat there, and to be honest with you, it ruined me for three, four months. I felt like a huge failure, I doubted everything about myself.”

What followed was a spell on the bench for the Black Cats. but O’Nien refused to give up and got a key copied for an astro turf pitch at the Academy of Light to do extra solo sessions with the goalkeeper coach. He was swimming in morning before training and doing extra weights sessions in a bid to rectify his disappointing debut and increase performance levels when next called on by Ross.

It culminated in his first goal for the club in a 2-0 away win against Shrewsbury, and he has never looked back – even if he was almost too tired to celebrate.

“My first goal against Shrewsbury – I trained that hard to get it all right because I didn’t think I was going to play,” he explained. “I was so tired, my first touch was the heaviest you’ll ever see, my second touch was a tackle, and Lynden Gooch then played the ball in behind for me.” I aim for the bottom left and drill it into the bottom right.

“I then go to celebrate, and I nearly collapse from exhaustion from training.”

“I don’t have a Sunderland career unless I get dragged off at half-time.” That is the driving reason behind where I am today. It taught me all I needed to know.”