The 37-year-old, a veteran of 249 games for New Zealand Knights, Wellington Phoenix, Gold Coast United, Melbourne Victory and the Jets, has not played since he tore a calf muscle in Newcastle's 2-1 loss to Sydney FC on January 10.

With 12 regular-season games left, he is expected to be sidelined for at least another two or three weeks, and once he is cleared to resume will need to dislodge Lewis Italiano from the starting line-up.

The former New Zealand international needs another five games to rack up a half-century of appearances for Newcastle.

Troubled by injury in the pre-season, he admitted in a club statement that he was struggling physically to maintain the high standards he sets for himself.

"My body is getting to a stage where it won't allow me to train at the level I feel like I need to be at, and that's what's prompted me to pull stumps at the end of the season," he said.

"I've made this decision early and informed the club so they have enough time to plan for next season, and I'll do everything I can to help Lewis Italiano and Noah James show they are deserving of contracts.

"I'm extremely proud of the career I've had in football across nearly 20 years, and there's no place I'd rather finish than here in Newcastle.

"While the wins and losses come and go, the friendships I've made will last a lifetime.

"I'm so fortunate to have found a mentor in Lawrie McKinna, and along with the support of Professional Footballers Australia I'm able to confidently transition into the next stage of my life.

"I have a real passion for coaching and I'm excited at the opportunity to pass on my knowledge."

There has been speculation linking him to a coaching role with incoming A-League franchise Macarthur FC.

Newcastle chief executive Lawrie McKinna said Moss had provided great value since arriving at the Jets in 2017-18. "Mossy is a top professional, and a top person who will give his all until the end of the season," McKinna said.

"Since arriving in mid-2017, he's been an outstanding representative of our club and for the city of Newcastle both on and off the park. We're looking forward to seeing Mossy recover from his injury and get back in action for the remainder of the season."

Only Ben Kennedy (114 games), Mark Birighitti (77) and Ante Covic (54) have played more games in goal for Newcastle than Moss.