The men's 4x100m athletics relay team's bid to qualify for this year's Gold Coast Commonwealth Games has been hit by an injury to key member Hariz Darajit, the current fastest man in Singapore.

The 19-year-old Temasek Polytechnic student suffered a complete tear to his right anterior cruciate ligament after he fell in his home last Christmas Eve. He is undergoing surgery next Tuesday at Singapore General Hospital and will be out of action for between six and nine months.

Hariz, Calvin Kang, Ariff Januri and Timothee Yap clocked the team's season best of 40.22 seconds at the Asian Track and Field Championships in India last July.

While it falls short of the Commonwealth Games qualifying time of 40.17sec - the sixth-place timing at the previous Games as mandated by the Singapore National Olympic Council (SNOC) - it is within the 2 per cent threshold of Singapore Athletics' internal selection criteria for nomination to the Games.

"At first I didn't think it was so serious, since the swelling came down," said Hariz, who was part of the 4x100m team who clocked 40.93sec to finish sixth at last August's Kuala Lumpur SEA Games.

"I am a bit sad because I was doing well (in pre-season)... but I am just focused on getting back on my feet, and will definitely be supporting my team-mates from the sidelines."

National men's relays coach Hamkah Afik, 45, was devastated to learn about Hariz's injury.

"Everything was going so well during the general preparation phase, he even clocked a personal best of 10.71sec during the Pol-ITE meet in November," said the former national sprinter, who is also Hariz's personal coach.

"He was in the best shape of his life and we were looking at him doing 10.55sec in February."

It has led to uncertainty surrounding the team's involvement at the April 4-15 Games in Australia.

Hamkah said the time frame was a bit short for the new quartet as a lot of analysis - from ground speed to who is more suitable in which positions - need to be done to get the team into optimal form.

Before Hariz's injury, Hamkah had also targeted qualification for the Aug 18-Sept 2 Asian Games in Indonesia and for the team to go below 40 seconds; the national record of 39.24 was set by Kang, Gary Yeo, Lee Cheng Wei and Amirudin Jamal at the 2015 SEA Games at home when they won the silver medal. Of that quartet, only Kang is still active.

Hamkah said: "The target was to go sub-40 and reach the final in Indonesia, and I can't change that goal just because of one person, it wouldn't be fair to the rest.

"We will have to overcome this challenge, get the best squad we can and focus on the process."