SINGAPORE - Mahathir Azeman must have wondered for a period if time moved slower for him than for everyone else.

For one, the Hougang United midfielder watched as other players walked through the doors at the gym at Jalan Besar Stadium, completed their rehabilitation, recovered from injury, and returned to playing.

"But I was always still there," the 23-year-old said with a wry smile. "One of my former teammates even joked with me and asked if I got offered a job at the gym since I was there all the time."

His injury nightmare over the last four years is no laugh. During that time, he has spent almost three years on the sidelines as a result of tearing the anterior cruciate ligament (ACL) in his knee a staggering four times.

A full tear of the ACL - one of the key ligaments that helps stabilise the knee joint - will sideline a footballer for a minimum of eight months, and sometimes even for more than a year. Thirty years ago, it was considered a career-ender.

This is what makes Mahathir's comeback story all the more astonishing. He is set to line up for Hougang on Tuesday night (August 27) at the Jalan Besar Stadium against last year's champions Albirex Niigata, where a win will lift them to the Singapore Premier League (SPL) summit with just three games left.

The Cheetahs, chasing their maiden SPL title, are in good form and have won five of their last six games. Mahathir has started in their last two wins, and scored in both.

Said Hougang coach Clement Teo: "Mahathir is a forgotten boy to some, but I have no doubts over his ability.

"He has shown he can contribute to the team and I'm very happy for him. And I'm confident he can do better."

Each of Mahathir's four ACL tears came with added disappointment for the former national youth team star, who rose to prominence at the 2011 and 2012 Lion City Cup.

The first, in 2015, occurred in his right knee and ruled him out of that year's SEA Games on home soil.

The second, in early 2017, was when his left knee buckled in an AFC Cup match for Home United, a platform he thought could help him re-establish himself. The third was when that same ACL snapped again, in the gym, after almost a year of rehab.

"That one really hurt," he said. "I had worked so hard to get back to that point, but even that was not enough?"

This left him without a club last year. Instead of letting his head drop, he decided to take up a one-year diploma in sports and exercise science course offered by PSB Academy, in part so he could learn more about recovery.

This was where he learnt about the psychological aspect of recovery, such as "self-talk". Videos chronicling the recovery of top athletes like Spanish footballer Thiago Alacantara and National Basketball Association star Derrick Rose from ACL setbacks, were also helpful.

"So many people have played a part in building me back up," reflected Mahathir.

They include Football Association of Singapore (FAS) physiotherapist Nurhafizah Sujad, its former strength and conditioning coach Matt Jones, and also current Hougang teammate Fazrul Nawaz, a PSB Academy ambassador whom Mahathir grew close to while undergoing his diploma course.

National striker Fazrul, 34, praised Mahathir's humility and said: "He has a really positive attitude, never gives up, trains hard, and despite the setbacks, has always shown the determination to come back stronger every time."

Mahathir suffered his fourth ACL injury - a partial tear of the left knee - in March this season in only his second appearance for Hougang, but past experiences taught him to be "calm" and he has since fought back to regain his place in the Cheetahs' starting XI.

"The biggest thing I've learnt over the last few years is that sometimes you just have to accept things," he said.

"It's how you react that's important, not asking why something happens to you."

And a star turn in his team's title charge is a fine reaction, to make up for all that lost time.