Just three summers ago, the Blades were bumbling along in League One and badly in need of a saviour.
Chris Wilder, the boyhood fan who had built a good reputation in the lower leagues, would prove to be that man – as the two promotions in the intervening years have since shown.
But things could have been very different had Wilder stuck to his original plan to become Charlton Athletic’s manager in 2016 rather than be swayed by an 11th-hour offer to take charge at Bramall Lane. As Duffy, a key figure in that success for the Blades under Wilder, knows very well.
“I was the gaffer’s first signing here,” said the Liverpudlian with a smile to The Yorkshire Post yesterday at United’s pre-season training camp in the Algarve.
“It was a strange one, He was close to going to Charlton, everyone knows that. I had already spoken to him and Knilly (Alan Knill, assistant manager). We had met.
“Then Sheffield United came in for them and the rest is history. To be honest, it was always better for me to sign here. It is a bigger club.
“But I would have probably ended-up following them down there (to Charlton). I am not going to lie about that. But I am delighted they chose this club. A match made in heaven.”
That ‘match’ was further cemented earlier this week when Wilder signed a new three-year contract.
It was a welcome development during a summer that has seen the 51-year-old understandably linked with a host of jobs.
“Brilliant that the contract got sorted,” agreed Knill, who also worked under Wilder at Northampton Town and is expected to agree his own new deal in the near future.
“It was important for the club to get the manager done. He is the leader. He has brought back an identity to the club, which was obviously needed.
“Now, he signs a new contract. He was manager of the year, he got us promoted – that means there are suitors out there for you. That puts everything to bed.
“We can now get on with the job and look forward to our first season in the Premier League.”
Considering the miserable season that preceded Wilder’s arrival at the Lane, United kicking off next season at the same level as Liverpool, Manchester City and Chelsea seems scarcely believable.
But, as the thousand or so fans who are expected at tomorrow night’s friendly against Real Betis in Faro will readily attest, it is the reality.
Much work is going on to get the Blades ready, both on and off the field. Record signing Luke Freeman has already arrived from QPR, while Phil Jagielka is back at the club where it all began for the former England international.
Further captures are planned with Dean Henderson expected to return on loan from Manchester United, while strikers Ollie McBurnie and Neal Maupay are very much on United’s radar.
Ravel Morrison is also on trial with the club in Portugal, though the former West Ham United midfielder has had to sit out training the past two days with a foot problem. A decision on Morrison’s future is expected to be taken after the return to England on Saturday.
Asked about whether United can maintain the recent rate of progress during the three years of Wilder’s new contract, assistant Knill added: “When we came here, there is no way we thought, ‘In three years, we will be in the Premier League’. But we have proved it can happen.
“That said, those three years have gone. In these next three years, we need to establish ourselves as a Premier League team.
“Sheffield United has been there before but did not stay there, for whatever reason. Now, we need to do that. That is the aim.
“Tough as it might be, we think we are capable of doing it. Bournemouth and Burnley are the examples.
“I do, though, think, ‘Yes, those clubs are really good’. I also look at their transfer policies, which are similar to how we look at players.
“But we will go and do it our way. We have a way of playing. It is something me and the manager enjoy watching. We are quite sure the supporters enjoy watching, too.
“It is the Sheffield United way. We attack teams, no matter what. I cannot see that changing too much. We look at the opposition and appreciate the quality. But we are going to have a go at it.”
As for Duffy, he remains so glad that his manager chose the Lane and not The Valley three summers ago.
“From day one the gaffer made it clear what he expected and wanted,” he added. “That approach has been very successful. Long may it continue.
“There will be big games coming up in the new season. It is not too far away now and we are preparing right. We play a unique way. Hopefully, we can catch a few teams out by doing that this season.
“It is the best league in the world and we want to be ready. We are all excited, even if you don’t really know what it will be like until you are in it.
“We don’t want to build it up too much because that can affect your performance. Just keep relaxed and the rest will take care of itself.“