To see Popa's career over the years...

To see Popa's press conference as it happened...

Popovic, 35, said he made his decision last Friday night after Sydney's game against Wellington and communicated his decision to coach Kosmina on Saturday.

The 59-times capped Socceroo who played in the English Premier League with Crystal Palace in a career spanning over 18 years, said the decision was related to his ongoing injury problems.

"It was an easy decision," he said this afternoon. "I promised myself when the day comes when I feel I've lost control what my body can do and I can't reach the expectations and standards of myself, I'd retire.

"My family when I told them were a little bit surprised I didn't wait until the end of the year but as an athlete you just know... you just know when the time is right."

Popovic aggravated his hamstring last Friday night in the first 20 minutes of the game. The injury that would've seen him sidelined for three to four weeks. It helped him make his decision.

"The injury is more than that," he said. "It's probably chronic wear and tear over the years. Something that I've lost control over.

"Coming back and hoping it'd get to train at the intensity required for the A-League ... I knew the time was right."

Popovic added that he found it hard to tell his teammates of his decision this morning, saying they were shocked at the news.

He added: "You kinda feel like it's unfinished business but I'm more than comfortable with my decision."

Kosmina said he didn't try to talk his skipper out of the decision, but was delighted he was staying on as an assistant coach at the club.

Short-term Sydney will look to Steve Corica to lead the side on the park but Kosmina said he'd take some time to look at long-term replacements for the skipper's armband.

He admitted he had no names in mind for a replacement for Popovic at the back of the park, but would initially be looking at the club's existing squad and youth team.

At the conclusion of the press conference, the assembled media warmly applauded Popovic.

To see Popa's career over the years...

To see Popa's press conference as it happened...