HE is the footballer at the top of his game. He was a man who struggled to get to the top of a flight of stairs.

The transition between epithets has taken five years and limitless resilience; Craig Gordon having navigated despairing thoughts and physical setbacks to reach a level of fitness and football which has brought him remarkable success. The goalkeeper was once unable to walk without feeling debilitating pain. He has just helped Celtic to run away with a league title.

When I caught up with him at the club’s Lennoxtown training base to record this Big Interview, Craig revealed just how low he felt after leaving Sunderland in 2012, and what it has taken for him just to play football again, let alone win trophies.

He was released by the Black Cats after suffering a second tear to the patella tendon in his left knee. Having undergone an operation to repair it only five months earlier, a surgeon told Craig that there was little to be gained from going back under the knife.

He would have to tough it out as the tendon healed naturally – a process which could take up to two years.

That prognosis failed to account for the daily discomfort his injury would cause, with the simple act of moving around the house being accompanied by constant pain in his knee. When Craig went on holiday to New York, he struggled to make it to many of Manhattan’s prime tourist spots.

“When I left Sunderland, I thought that was it for my career. I didn’t see a way back,” Craig says in the podcast. “The pain was so bad I found it difficult to get up and down stairs – I couldn’t take any weight on my knee at all.

“That was daily life; every day it was painful to walk around. I thought: ‘It this what it’s going to be like from now on?’ For a good few months I didn’t do anything at all.”

Such enforced inactivity was in stark contrast to the incredible leaps Craig had made earlier in his career. He won a Scottish Cup with Hearts and established himself as first choice for Scotland, before moving to Sunderland for £9 million – a British record transfer fee for a goalkeeper.

Injury had forced him to take the gloves off, and he decided to fight to save his career. Craig researched different treatments to help aid his recovery and set off for Barcelona and then London to have a series of injections.

“I had four PRP [platelet-rich plasma] injections in Barcelona and had high-volume injections in London,” he says. “That is basically when they blow up the area round about the tendon to squeeze it. That kills the blood vessels which are growing into and causing the pain.

“They all worked to some degree and I began steadily to improve. It took a whole season but I was able to start doing some exercise again.”

The road to recovery took him to Glasgow, where he teamed up first with Rangers. Physio Steven Walker had nursed Norwegian midfielder Thomas Kind Bendiksen, pictured below, through a similar injury and devised a rehab programme to help Craig.

“We just took it really slowly,” the goalkeeper says. “It took almost a full season until I was back out on the training field, there were a few teething problems, but overall I was managing to get through three sessions a week.

“There were moments when I didn’t think I could take it. There were a few little setbacks, when I thought everything was going okay and then I would do a couple of football sessions and it would get sore again.

“There were definitely times that I didn’t want to go in, that it was too painful and too tough. But my wife [Jennifer] would remind me that I didn’t have anything else to do, that I should get out the house and do it. So I did. I wanted to give it everything.

“On the back of that I managed to get a deal at Celtic – this is my third year here and I have no problem with the knee whatsoever.”

He feels like his old self again. He plays as though he is even better, winning three straight titles and two League Cups. Craig has also been the subject of two bids from English champions-elect Chelsea.

But the Celtic goalkeeper says that reclaiming his career is a triumph which will not be surpassed. “Getting back from where I was will probably be my greatest achievement,” he says.