LIAM Jones thought his career was over in 2017.

For a couple of weeks last season, he was suddenly and shockingly having similar fears.

His concerns three years ago were justified, having been uncontracted and struggling to establishing himself as the main marking target in both the forward lines of the Western Bulldogs and Carlton.

His worries last season were more unexpected and far more serious.

After reinvigorating his footballing life as an intercept defender with Carlton and in the prime of his career down back, Jones was involved in a sickening clash of heads with North Melbourne's Cam Zurhaar.

Jones was knocked out cold, with medics carefully helping the 199cm backman from the field after an extended period where the Marvel Stadium crowd fell under a hushed silence.

He would miss the next seven weeks, undergoing a series of vigorous scans and tests where doctors delivered significant doubt Jones would ever be able to play football again.

"It was worrying," Jones told AFL.com.au from Carlton's pre-season training camp in Mooloolaba.

"I didn't feel too bad for a day or two afterwards, but all of the symptoms started hitting me … the dizziness, shocking memory, not being able to do anything.

"There was a period of time where there was a question mark about whether I'd be able to play again because the symptoms were hanging around for so long.

"I had a lot of scans and the club and the AFL handled it really well in terms of my testing and all of the protocols I had to go through and catching up with specialists.

"I flew my dad down from Darwin to catch up with the specialist and there was a bit of concern there, but, thankfully, I got the opportunity to come back and play again.

"I've been symptom-free ever since and there's been no reoccurrence of it. I'm really thankful because it was a worrying time, but I got through it. It made me miss football, but it made me want to play it even more and be grateful for it."

Jones doesn't remember anything from the incident. In fact, he barely remembers anything from the day. Occasionally, he can vaguely picture himself driving to the ground, but that's it.

"I felt out of it for about three weeks," he said.

"Getting up from a seated position or from laying down, I felt dizzy. It felt like I was about to fall over and that my head was in a washing machine, just spinning constantly.

"I had a really bad memory and I felt like I was out of it, like I was half-asleep."

Of course, last year wasn't the first time Jones had endured fears about his career ending.

Having managed just 16 goals from 17 games in almost three years with Carlton following a much-scrutinised trade from the Western Bulldogs at the conclusion of 2014, Jones thought his time in the AFL system was coming to an end.

Then 26 years of age and stuck in the VFL, Jones was approached by Northern Blues coach Josh Fraser about the potential of moving into the backline. With just six months left on his contract – and, seemingly, his time at Ikon Park – he threw caution to the wind.

After a number of impressive defensive performances, he was recalled to the senior team where he effectively shut down Greater Western Sydney's Jon Patton and Gold Coast's Tom Lynch in successive weeks.

"I was in the last year of my contract and, to be honest, I was probably lucky to even get to that year," Jones said.

"I saw it as my last year of football, so I just wanted to take myself back to when I was a little kid and realise how much I love my footy and how lucky I was to go and kick the footy every day. I really wanted to just enjoy my time at the club.

"Josh Fraser put the belief in my ability to play anywhere, so I was playing in the ruck and in the forward line, but I ended up going into the backline.

"I was getting this praise for what I considered to be not that good. I was just spoiling the ball and following my bloke around, but everyone was saying, 'hey, you're good in this position'.

"I was used to trying to mark and kick goals, so I didn't really see what I was doing well. But I was really grateful for the opportunity."

Within an instant, a two-year deal with Carlton was tabled and signed. Jones' career, so often mocked externally, was suddenly on the rise and earning the praises of the football world.

"I was asking myself what had happened," Jones laughed.

"It's amazing. I try and tell the young guys now that one week or one game can change your life. I felt it all happened through good preparation and a good mindset, being ready to go when my opportunity came. It's amazing how the footy world can change."

Ask anyone in Carlton's defensive set-up to take you through such preparation – that Jones himself says he constantly pores through – and the response is usually met with a referral to his impressive 'black book' on opponents.

Jones has filled pages and pages of that 'black book' with comments and observations on virtually every forward in the competition. The markings are scratched out, amended, improved and added to with each passing game.

"Literally everything is in there," Jones said.

"Where do they get the ball? I'll watch every single inside 50 that they have to see their patterns and see where they take their marks.

"What don't they like and who has played well on them? I'll look at some really good defenders that have played on these guys and look at what worked, what didn't work, where they got them.

"The next game, I'll look back at myself the last time I played them and see what worked. Normally, forwards have patterns, so I'll use that sort of stuff and try to fix up the mistakes that I might have made the first time to help myself."

The success Jones has reaped from that preparation, combined with last year's realisation that his time in football could suddenly end so abruptly, is now providing him with the motivation to make the most of his remaining years in the game.

"I feel like I'm 21 and just getting started," Jones said.

"I'm 28, but I feel like I've got so much more football left in me because I'm still learning so much.

"The game rewards you … all of the positive things that have come through from my hard work, it's made me want to work harder and see what I can achieve."

It's time to become a member. Join HERE or by calling 1300 CARLTON.