Tony McCoy paid tribute to the retiring Jason Maguire by labelling him as one of the toughest competitors in the weighing room.
Grand National-winning jockey Maguire, 36, called time on his career in the saddle having not ridden competitively since February 2015, after a fall at Musselburgh.
Prior to that he suffered life-threatening injuries on the eve of the 2014 Cheltenham Festival at Stratford.
Maguire underwent surgery in April 2015 for slipped discs in his back and while he has been riding out for the likes of Kim Bailey and Tom George, he was often left with pain in his leg.
Having ridden as first-choice jockey for Paul and Clare Rooney, during his time off he has been acting as their racing manager and will continue that role full-time.
Maguire finished second to McCoy in the 2012-13 title race, and the 20-times champion said: "It's something he's been suffering with for some time, pretty much since the Stratford fall.
"I know that was not his back, but it deteriorated from there.
"For the last six months he was riding in unbelievable pain, he was having to travel to the races lying down in the back of cars it was hurting so much.
"People don't realise a lot of the times what the lads are going through just to get to the races."
McCoy went on: "He was an unbelievably tough competitor and, if anything, he was getting better with age.
"I always judged myself by numbers and his numbers were on the up, he was at a point in his life where statistics showed he was getting better.
"It must be tough being forced to retire, I was able to make the decision myself, but he will be a huge asset to Paul and Clare Rooney now because he has a great knowledge of the game."
Maguire's agent Chris Broad said: "It's disappointing, but the news has been expected, to be honest.
"He was a top, top top-class rider, it wasn't long ago that he split AP McCoy and Richard Johnson in the championship - that's how good he was."
Maguire won the 2011 Grand National on the Donald McCain-trained Ballabriggs and enjoyed Cheltenham successes on Galileo (2002), Peddlers Cross (2010), Cinders And Ashes (2012) and Son Of Flicka (2012).
Broad added: "He's had some memorable days, no one can ever take a Grand National win away from him and he's enjoyed good days at Cheltenham, too.
"He's been a very good man to work with, he lives locally to me and we get on well but unfortunately his body is no longer responding how he wants.
"There is a life after racing and luckily for him he has already got his lined up with the Rooney job.
"Obviously he'll still miss it, and it is very different being forced to retire rather than retiring on your own terms. It's much harder to cope in this situation when the decision is made for you.
"He was very stylish and very strong, but there comes a time when it has to end.
"I went to hospital to see him after the Stratford fall.
"After seeing the state he was in there anything was a bonus after that and while it's disappointing for him it's ended at least he's in one piece, if not quite 100 per cent.
"He's been one of the best."
Maguire began his career in England with Tom George, who supplied him with his first Festival winner in Galileo.
"We go back a long way and had a lot of success," said George.
"We had a bit of a parting but the last few years we teamed up again and I'd say he's ridden over 100 winners for me.
"He came to me from Ireland, I told someone I needed a claimer who was a good jockey and Jason arrived on my doorstep. I only had about 12 horses at the time.
"I bought him his first car for £300. He got his money's worth out of it but it broke down one day on the way home from Bangor and I never saw it again!
"You could never fault his riding, he was very strong.
"I actually haven't had a conditional since him because I always compared them to him and they weren't a quarter as good as he was, so I just never bothered.
"The most important thing is he is getting out in nearly one piece.
"He's got a nice set-up where he is, just down the road from me and I'm sure I'll see a lot of him."