The 36-year-old, who has been at Blues for the last four-and-a-half seasons, will now take a break from the game to pursue business interests in Spain.
The former Republic of Ireland international was ruled out of the 2012/13 season with a knee injury last summer and now, with a glittering career behind him, Carr has been forced to finally call it a day.
Announcing his intention to hang up his playing boots, Carr explained to bcfc.com: “I am going on 37 and now is the time to bow out.
"I felt OK in pre-season but unfortunately my knee just crumbled away. It was unfortunate for me and the club. We knew there was a chance something could happen, but we didn't think it would be that early. It just wasn't meant to be in the end.
“There was always a very slight chance that I could come back from what the surgeon had told me. Three ops in 18 months on the knee - it was telling me it had had enough, basically.
"I can do the bike and all that in the gym, but I think that's as far as it goes. I’d now like to thank the medical staff at the club for all their help and a special mention to Dave Hunt for putting up with me during all of those one-on-one sessions. They've all been great to me.”
Of course, this isn't the first time that the Dubliner has announced an intention to end his playing days. After a trial period at Wast Hills, Blues plucked Carr from premature retirement back in February 2009, initially on a one-month contract.
The right-back never looked back and went on to become club captain and an integral part of the side that gained promotion to the Barclays Premier League. Carr’s committed displays for Blues quickly made a mockery of the defender’s initial struggle to get a club.
Having been at this crossroad before, Carr admits that the feeling is different on this occasion.
He continued: "The last time I stopped playing I was 31 and it was because I couldn't get a club. This time it’s different.
"If I was 31 again, I'd be very disappointed but it was lucky I got back into the game and had a couple of great years here, which I thoroughly enjoyed and never saw happening when I originally finished. So there's a lot of highs that came with it.
"Obviously we had the low point of getting relegated and then since that it has just gone slowly downhill for me, injuries have just picked up.
"I am 37 in August and I've had a good innings in the end. My knee has lasted out quite well but it comes to the stage where enough is enough with it.”
So what next for the former Tottenham Hotspur and Newcastle United man?
“I’ll be heading off to Spain for a few years and see how it goes. I’m involved with Sala Group Holdings who run two restaurants in Marbella, the beach club on the front and we've got a nightclub, which was open last year.
“It’s getting bigger and bigger and we’re hoping to move that abroad. We’re speaking in Dubai at the moment about getting premises out there. We just want to keep getting the brand bigger and bigger and hopefully I can help them promote it.
“I want something different in my life and something different the kids can experience as well.”
There’s no doubting that Carr will always have a special place in the hearts of Bluenoses for being the captain that lifted the Carling Cup at Wembley in 2011.
And the feeling is certainly mutual.
"I'd won the cup before with Tottenham but for me to come back, after being out of the game, to get back into the Premier League straight away and win the cup the following season, it was just unbelievable,” he reflected.
"Equally for my kids as well because they were younger when I won it the first time. They have loved it here in Birmingham and I have really enjoyed it. This club will always be a special place for me.
"The fans have been brilliant with me since I came in and I have had a great relationship with them. I will never forget that day lifting the cup. It was a big, big thing for me.
"It was just unfortunate then that we couldn't carry the season out but that's football I suppose."
While Carr feels now is the right time to give up the game that has given him a 20-year career, he does feel a certain amount of regret at not being able to repay Lee Clark’s faith in him last summer.
When Clark took charge of the club last year, one of the new manager’s first priorities was to offer Carr a new one-year contract and ensure that he retained the club captaincy. Sadly, it didn't pay off with Carr’s campaign over by the time pre-season 2012 was complete.
“The manager has been excellent with me considering he gave me a year and took a little gamble on me. Nothing came of it, unfortunately, for me or him.
"I don't care who was in charge this year - that job was tough for the manager. He's still a young manager and he's probably learning a bit.
"As you saw in the end, we weren't a million miles away from the play-offs which was really gutting because if we had started just a little bit better and picked up a couple of results at the start then we would have been there."
"That gives you a lot of hope for next season.”
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