The enjoyment had gone and the job he had dreamed of doing as a boy had turned sour, not helped by a couple of managers whose approach he could not abide.
So, Glennon did what most footballers dread to do the most; he started to think about life after football and how he was going to make a living.
Which is how, at the age of 36, the Stockport-born stopper is now the proud owner of a thriving barber’s shop and a hair and beauty lounge in West Yorkshire.
Building up two businesses from scratch has not been easy, but stepping away from full-time professional football has also re-awakened his love for the game. For that, he has FC Halifax Town to thank.
“Life is good at the moment,” Glennon told The Yorkshire Post ahead of Halifax’s eagerly-anticipated FA Cup first-round derby with Bradford City.
“I had been going through a stage towards the end of my full-time career where I thought, ‘I am not enjoying this any more’. Basically, I’d had enough.
“So I decided to do something different. I still enjoyed playing, but you work with certain managers and get to a certain stage in your career when you realise the reason you came into football is not there any more.
“It was time to move away and I needed to start thinking about the future. Funnily enough, I was at a barber’s when the topic came up.
“The barber was asking what I wanted to do when my football career was over and I wasn’t really sure.
“I had a few ideas in mind but I was then told about this hairdressers’ academy. I thought, ‘Why not?’ and went along. I loved it. The guy running it was a real eccentric New York barber and I threw myself into it.”
Glennon’s switch from donning the gloves on midweek days to picking up scissors and a comb came in the wake of his release by Stockport County in January, 2012.
Before long, he had bought a salon in Emley, Huddersfield, and renamed the business ‘G27’ in honour of the squad number he had worn when playing for the Terriers.
His skills quickly proved a hit and the shop was busy. Former team-mates even popped in, including Town legend Andy Booth. “I can’t say his haircut is one of my more challenging,” says Glennon with a laugh.
Things went so well that he was soon opening up the G27 Hair & Beauty Lounge 500 yards away. “It has been hard work and a lot of hours,” says the 36-year-old, who spends his day at ‘G27’ and leaves the work at the Beauty Lounge to others.
“But building something from nothing has been really satisfying. The shop is great fun. The customers are great and we have a right laugh most days.”
Running a Huddersfield version of Desmond’s, the fictional barber’s shop featured in the hit Channel 4 show, has also allowed Glennon to regain his passion for playing football.
“When I decided to stop playing full-time,” he says, “I did say I would like to keep playing on Saturdays. I still enjoyed that part.
“The chance came up at Halifax (in the summer of 2012, when the club was in Conference North) and I jumped at it. Training was a couple of nights per week so things fitted in well.
“As soon as I joined, I found myself enjoying football again. It happened more or less straight away. I loved the challenge, too.
“When I first signed, the manager made a big thing about clean sheets. It took me four games to keep one and during every second of that time, he kept on at me.
“I liked that because the challenge was there and by the end of the season I had kept 24 clean sheets.”
Glennon, who played 17 times for Bradford during the 2009-10 campaign, has now made more than 100 league appearances for the Shaymen.
This has helped his career total of games edge towards 600 and that means he will take plenty of experience into tomorrow’s derby.
“I’ve been fortunate to have had some big days in the FA Cup,” says the veteran of 13 clubs. “Being part of the Huddersfield team that knocked (then Premier League) Birmingham out (in 2008) was a bit special. We played Chelsea that year, too. Obviously, it was great playing down there in front of 40-odd thousand. We also went in 1-1 at half-time, but I feel we could have played a little bit better than we did.
“Earlier in my career, I played for Carlisle against Arsenal. I was 21, had only played 10 games and they had Vieira, Bergkamp and Wiltord.
“Brunton Park was bouncing and Arsenal only just squeezed through. We just didn’t get that bit of luck you need in the Cup for a shock. Maybe we will against Bradford this weekend.”