The popular 33-year-old, who played in both of Perth's National Soccer League championships, will get the chance to farewell Glory fans on Sunday as he plays his 256th and final game against Gold Coast United at nib Stadium.

However, in a season that's slowly gone from bad to worse for the club, Harnwell's retirement announcement was not without drama, as Glory inadvertently displayed a banner on their website on Sunday, indicating this would be Harnwell's last game, 24 hours before he was due to meet with the administration about his future.

Glory chief executive Paul Kelly apologised for the mistake, calling it a 'technical issue', but the bungle will almost certainly be interpreted by fans, already angered by the poor treatment of Andy Todd and Jamie Coyne, as a sign Harnwell was pushed.

Harnwell, though, declared this wasn't the case, saying time simply caught up with him.

"This is the best job in the world, you never want to give it up," Harnwell said.

"But I just felt that the time was right. The way the club's been going and the way they want to go in the future, I just felt it was time to move aside and let the young blood through.

"In the past few months I haven't enjoyed myself like I should have as the years of training, travelling and sacrifice have caught up with me.

"Although this will always be my club, with the new direction we're heading next season, a new team will be built."

Harnwell said the decision became clear to him after being red carded during the 2-1 loss to Central Coast a fortnight ago.

"After I'd been sent off, I was frustrated with myself, I was frustrated at the team, the way we'd been playing," he explained.

"I was just at home and I turned to my wife and I said, 'I think that's it, I think I'm done'.

"Obviously you don't make decisions like that on the spot. I had a lot to think about and to talk to the club about (but) over time I think my gut was right.

"When the crunch came down to it, we could have kept talking another week or two. But you know, the time was right and I made my decision and that was it, it was final.

"I'm happy with the decision and I think the club are as well.

"It's a big weight off both our shoulders that I'm not still hanging around and lingering and seeing what's going on.

"It's a good clean break and it's an opportunity this Sunday to thank the people that have supported me for so long."

Harnwell added he had not been specifically told by interim coach Ian Ferguson that he wasn't in the club's plans for the future, but did say he would have been a 'low priority' to be re-signed despite impressing in the games he's played this season in a central defensive role.

The Glory veteran also felt that his conditioning was good enough to have kept on playing.

"Physically, yeah, absolutely," Harnwell said. "I think I've played enough games this season and my performances have been good enough that if I wanted to, I might have been able to go on again, but I just thought it wasn't right.

"I'm under no illusions, I was a pretty low priority and looking forward to next season, the club's obviously got to go out and find some new players."

"(But) I still love playing," he said, revealing he would return to play for WA premier league side Sorrento.

"I still really love playing, running out in front of the home fans and that dream of playing in front of your 40,000 at Subi again.

"That's always been a highlight of my life and it's something I'm never going to experience again."