The former Millwall keeper won promotion with the Lions in 2000, bagged two international caps and played 21 times in the Premier League with Fulham from 2005-07.
But he has sat on the bench in League Two – and also seen first-hand what can happen to clubs when the cash is not carefully watched.
He was at Bolton when owner Eddie Davies finally stopped pouring money into the company which owned Wanderers – and wrote off £175million of its debt.
Warner said “Pretty soon after that it ground to a halt and that shows just how badly it was being run.”
Davies even wrote a cheque for another £5m shortly before his death in 2018 to stop them going into administration.
Players are best focusing on what they can control at times of crisis, says Warner.
“Throughout my career I didn’t take any interest in the stuff outside my day to day job,” he said. “That was the way I operated “I have played with lads who looked at the finances and talk to directors but I just looked to train, do my job and look forward to games and only paid attention to the team and how we are playing.
“Bolton looked a shrewdly run club. They always seemed to be punching above their weight and had world-class players with a few years left in their legs.
“But judging by what happened afterwards, we all realised they were hemorrhaging money left, right and centre. Eddie Davies was writing cheques so often – and as soon as he pulled out, it turned into a bit of a mess.
“By the time I left, they were back in the Championship. I was only working as a coach in the academy then, so I kept separate from the first team.
“A lot of players have an interest in companies they work for and I can understand that – but I just didn’t have the brain space for it.
“You have to look after yourself and if there are extra responsibilities like a family it adds to your worries.
“As long as the team was fine and I was playing on a Saturday – and hopefully getting paid – I tried to keep out of it.
“I’ve been really lucky because I haven’t had many times when I was paid late. The worst was a three-month delay – but at that club, I knew I was dealing with a rogue. Players do get into these situations.
“I have two kids now age 10 and 11 and had my family at the end of my career, so did not have the worries that some players with younger ones do.”
Warner moved clubs 19 times during his career – after earning the nickname of Bonus for sitting on Liverpool’s bench for five years, earning extra cash when the Reds won, without actually playing.
But Millwall fans will always know him as Denzil, after the Only Fools and Horses character – also a Merseysider – of that name.
A favourite chant of the time was “Denzil, what’s the score?” which would prompt him to raise the appropriate number of fingers.
He joined the Lions in 1999, after loans at Swindon, Celtic and Aberdeen, and would miss just one game in the 1999-2000 season as the Lions finished 5th in Division Two before losing in the play-offs.
He would play a total of 225 times for the club, was crucial in the club’s title winning campaign the following season as Millwall won promotion back to Division One, finishing with a record 93 points.
The following season was a low point, as the Lions lost their play-off semi-final against Birmingham thanks to a late John Stern goal.
The end of his Den time, when it came, was sudden and poorly timed Wolves were showing interest and wanted to sign him in January 2004 before the transfer deadline but Millwall also wanted to keep him and manager Dennis Wise kept asking him if he would sign a new deal.
“I did not want to leave – I wanted to stay but Millwall were not offering what I thought I was worth,” said Warner.
“But I got a neck injury. I came back after six weeks but then broke my knee in training after a tackle by John Sutton – it was a stupid challenge. But you can’t do anything once it’s done.
“In hindsight it was probably the best thing because a lot of players were leaving and the team was being dismantled,” he said. “If I had stayed another two or three years I would have been involved in a relegation.”
He was chosen to walk out at the front of the team in the FA Cup final – but would never get such a long run in any team.
“My peak did not have a steady downturn – I fell off a cliff early,” he said.
“Millwall was the main point of my career. Regular football tailed away after I left The Den. My spell there was what I’m most known for, and where I had my most success – I was established player.”
Warner played for another 11 clubs and was on the bench for another four, including Charlton. Another was Leeds – where Wise called on him again on loan, only to replace him with another ex-Lions stopper, Graham Stack, when Warner’s form diped.
The keeper has also been goalkeeping coach at four clubs, including his current one, Accrington Stanley. But he is happy not trying to climb higher.
“I never had any interest in being a manager,” he said. “You get a lot of bluffers in football – and I would have had to have been a bluffer to be a boss.
“I don’t much like getting caught out so I never wanted to do that.”