Sinfield will end his decorated 19-year rugby league career with Rhinos at the end of this season and move to the Championship union side – now called Yorkshire Carnegie – on an 18-month deal.
The stand-off’s recruitment is seen as a major piece of the jigsaw as they seek a Premiership return for the first time in five years.
Though new to the code, with all his leadership and organisational quality plus stellar kicking game, the former England captain is seen as a natural fit.
Sinfield, 35 this Saturday, is coming towards the end of his playing days but Back, Carnegie head coach from 2008-2011, says he almost switched in his pomp.
In Back’s new autobiography The Death of Rugby, Carnegie’s then director of rugby Andy Key says ‘completely out of the blue he (Sinfield) contacted us to state he was interested in playing for Leeds Carnegie.’
Speaking to The Yorkshire Post, Back, who led Leeds to promotion in his first season but saw them fall out of the elite in his last campaign, added: “Kevin Sinfield was a quality rugby league player with all the attributes to make the transition to be a very successful rugby union player.
“On two occasions in both our second and third season he came to us and expressed an interest in coming across. He had ambitions to play at the highest level of union. We’ll never know if he’d have made it but we certainly talked about it. Yet at the 11th hour – both years and with no pressure from us – his mind was changed.
“One day he’d spoken to all his family and friends and they are behind him and then the next day he’s not coming at all.”
Back infers the Rhinos hierarchy would not sanction the move with Sinfield, who has led them to six Super League titles, three World Club Challenges and two Challenge Cups, too integral to their cause.
Rhinos chief executive Gary Hetherington was, of course, in charge of both clubs at the time.
Back, 46, believes Carnegie would have stayed in the top-flight if Sinfield had joined.
They lost their final game of the 2010-11 campaign 31-24 at Northampton, finishing joint-bottom with Newcastle but, ultimately, suffered relegation due to an inferior points difference.
“It was unfortunate and I think, if he’d come, Carnegie would have stayed in the Premiership another season,” said the British Lion.
“We will never know but going into that final game we needed to score four tries to get another bonus point – and we scored three.
“Kevin is the sort of player who could probably have made a difference in those circumstances.”
Back, who resigned after the relegation, is critical of the level of investment that went into Carnegie, insisting they could not realistically compete.
“It’s not about the environment or the culture because Stuart Lancaster has taken the exact same culture he created at Leeds to England,” he said.
“The difference is Stuart Lancaster has got the best players there, so ...
“If on day one we’d been told the budget you’ve set is unrealistic neither me or Andy would have signed to join Carnegie. The club, Andy and I, and all players and staff, were let down.”
Hetherington responded last night and said: “I can state quite categorically that at no time has Kevin Sinfield ever approached me to discuss a switch to rugby union or to leave the Rhinos.
“He has never been out of contract in all the time he has been here.
“Clive Woodward did speak to me when he was England coach, probably pre-2003, about Kevin’s potential to play union and Kevin told me, out of courtesy, that Clive Woodward had spoken to him but nothing else was discussed.
“When Neil Back was in charge, the club was in debt and its owners were Leeds Metropolitan University.
“When Leeds were relegated in Stuart Lancaster’s final season he had a rugby budget of £2.5m. When Neil Back and Andy Key took over and got us promoted to the top-flight, they had a rugby budget of £4m per season in the Premiership.
“That was significantly higher than any other time if lower than most other Premiership clubs.”
“The Death of Rugby”, published by Pitch Publishing, is available to buy via Amazon, Waterstones and WHSmith and you can follow the book on Twitter @NeilBack and @TheDeathOfRugby