But with his career in the balance, Hargreaves acted on the recommendation of a close friend, Steve Nash, the Phoenix Suns basketball player, to enlist the help of McKechnie, who has spent the past seven years as the LA Lakers athletic performance coordinator after saving O'Neal's career following an abdominal injury.
McKechnie said: "I treat broken down athletes who are almost like reclamation projects, but Owen gave this his maximum effort and threw everything into it unconditionally.
"He had what you would call a deep default posture, so we had to bring his body to a neutral posture through core movement.
"Without core strength, your body is basically trying to shoot a cannon from a canoe. In simple terms, muscles do not work in isolation – they work collectively to produce power, strength and co-ordination. In someone like Owen, when you have issues with your knees, the first step is usually to strengthen the quadriceps and the first reaction is to go to the weights.
"It's a fact that that process builds power and strength, but functional strength is the key and the leg muscles come from the pelvis.
"The quads, hamstrings, abductors and gluteal muscles all come from your pelvis, so all the muscles going into your thigh have a pelvic control. If you don't have a control of your pelvis, then first and foremost you are not going to have control of your knee.
"Owen had considerable loss of quads and control of his patella tendon, which led to the dysfunctional movement and issues with his knees."
McKechnie's methods involve intense concentration and commitment, but he admits that Hargreaves proved to be the perfect patient.
He said: "To get to where you want to be, you have to re-educate movement and correct the posture. That change takes four to six weeks. Continuously, for the first 3-4 weeks, Owen would work in front of a mirror and never come away from it.
"It starts from building one position, from a simple squat, to a drop-step and sidestep.
"The mirror gives visual stimulus all the time so he knows exactly where the core balance is. We would spend a minimum of two hours day doing this, but mostly three hours, even on Saturdays and Sundays."
On his return to United last month, Ferguson admitted his surprise at the progress made by Hargreaves and the optimism surrounding his recovery is genuinely high, only weeks after his prospects appeared bleak.
McKechnie added: "Is Owen OK to play? From a recovery perspective, yes he is, but from a football perspective, that's purely something for his coaches. But he has put himself in the position to play.
"He was with me for seven weeks and the last two weeks were basically on-field training, repeating the patterns of movement that we had worked on.
"We didn't touch a ball. I have no interest in the ball, I'm not a coach, but all credit must go to Owen. All I can do is hit the ball into Owen's court – he is the one who has to hit it back."
Interest in McKechnie's methods within the Premier League has been minimal, yet he admits he is keen to share his experience with English clubs. "Owen's quote to me was simple. He said, 'This should be in football. I can't believe it's not in football.' My programme is now used by 23 of 30 teams in the NBA, plus numerous teams in the NFL and NHL.
"I did a workshop last summer with Manchester City and spent time with West Ham about eight years ago. I would love to do a workshop with the Premier League."
An all-time great of NBA, ‘Shaq’s’ LA Lakers career was in the balance with an abdominal injury in 1998 before McKechnie spent two months resolving the problem. At 38, O’Neal is now oldest player in NBA with Boston Celtics.
Phoenix Suns point guard Nash recommended McKechnie to Owen Hargreaves, saying: Alex is not only a physiotherapist but a world-class movement specialist.”
Tennis legend Connors regularly used McKechnie’s services during his career in the 1970s and 1980s.