Sinfield, who led Rhinos to seven Grand Final wins, two Challenge Cups and three World Club Challenges in their greatest-ever era, returned to the club in July 2018 in the newly-created position of director of rugby.
Although he has enjoyed aspects of the job, he says it has moved away from what he envisaged and the plight of his former team-mate Burrow - who continues to battle motor neurone disease - only strengthened his belief that he must do something that makes him happy.
“I feel like I’m too far away from the rugby and too far away from performance,” said Sinfield, in a Zoom press conference this morning.
“I certainly got some perspective from Rob and it certainly hammered it home to me you have to do something you truly enjoy and get satisfaction from.
“It’s become very political, it’s become a lot of bureaucracy, it’s become a lot of red tape and in and around that there’s been a difficult 18 months for everybody (due to Covid) with cuts and budgetary things that have been implemented in every single business and every single walk of life around the UK and worldwide.
“It’s very much changed my role. It’s become very much administration - but not enjoyable administration!
“Without giving too much away and explaining how things have changed, it’s just become a role where I get no satisfaction whatsoever.
“I understand there’s a lot of people out there who don’t get a lot of satisfaction from their job and I understand I'm pretty fortunate I get to choose.
“But I do think it’s the right thing for everybody.
“The club is in a stable position, the club will continue to grow and get better and I’ll be firmly behind that supporting.”
Former England captain Sinfield - one of its most famous players and a Golden Boot winner - helped raise more than £2m for Burrow and the Motor Neurone Disease Association by running seven marathons in seven days last winter.
He received an OBE on Saturday partly for those remarkable efforts and will continue his charity work.
Sinfield, 40, added: “I want to stress I love the club and the sport and that will always be the case.
“It’s always in my heart and in my head. And I might be doing a role away from the sport but it does not mean my commitment, support and love for the sport will change.
“It’s just time to move on.
“I spoke to Jon Dutton yesterday at the Rugby League World Cup.
“I’m an ambassador there. I spoke to Ralph Rimmer, the CEO of the RFL, and made it pretty clear that I will support the sport however I can and will continue to do my best.
"As there are a number of former players the sport has who don’t work in the sport who continue to be great ambassador and champion rugby league and I hope to be one of those.”
Sinfield played rugby union briefly for Yorkshire Carnegie after retiring as a rugby league player when leading Rhinos to the treble in 2015.
He now returns to the 15-man code where he replaces Mike Ford as Leicester’s defence coach.
Tigers head coach Steve Borthwick said: “It is incredible to be welcoming someone of Kevin’s calibre and experience to our club.
“The vast and unique experience that Kevin will bring to our coaching means he is a great addition to our team. He is a serial winner and an inspirational character who possesses the hard-working and tough qualities we want at Leicester Tigers.
“This is an announcement everybody involved with Leicester Tigers should be excited about.”
On the Tigers website, Sinfield added: “I am really looking forward to this new opportunity in my career and the chance to work with Steve Borthwick, his coaching team and the playing group he is building at Leicester Tigers.
“It is a big challenge, but one that I know I am ready for and – after speaking with Steve – I am looking forward to joining the club at this stage on its journey and getting to work in Leicester.
“I am delighted to be able to join a huge club like Leicester Tigers with such a great history and supporter base.”