1) Matt Le Tissier (Southampton to Spurs, 1990)

A bittersweet regret to match the ending of Casablanca: what would have happened had Matthew Le Tissier joined a big club - or even Spurs, who came tantalisingly close to signing him in 1990. Many stories suggest that Le Tissier, a Spurs fan as a kid, even signed a contract before changing his mind and ripping it up with the permission of Spurs chairman Irving Scholar. Certainly it was the closest he came to leaving Southampton. Later there would be strong links with AC Milan, which is almost too exciting to comprehend, and also Chelsea, but by then Le Tissier was intractable in his belief that there was more to life.

Some will always deride him as the big fish who could only handle a small pond, yet others will argue that the absence of the sort of murderous ambition that has characterised the Premier League is a good thing; one that suggests, you know, humanity and a soul. Either way, it's fascinating and peculiar that the managers who wanted to sign him for Spurs and Chelsea - Terry Venables and Glenn Hoddle - were the same men who ostracised him when they took charge of England. Ironies don't come much more bittersweet.

2) Diego Maradona (Argentinos Juniors to Sheffield United, 1978)

In modern football, the Copperfields rarely mix with the Schiffers, but back in the day such is-he-really-going-out-with-them trysts were surprisingly frequent: the barely fathomable transfers of John Charles from Juventus to Leeds and Allan Simonsen from Barcelona to Charlton spring instantly to mind. Yet those would have knocked into the proverbial cocked one had Diego Maradona, then 17, joined second-division Sheffield United in 1978. United's manager Harry Haslam was a renowned wheeler-dealer with a good strong finger in the South American pie; even allowing for that, however, it's hard to buy this story. Most reports suggest that United could have had Maradona for £200,000, but missed out on the ultimate Sheffield steal and instead decided to pay £160,000 for Alex Sabella. It's a good story, but then so are Walter Mitty's.

A report in the Guardian in 1981, the day after Haslam was sacked by United, said he had worked Argentinos Juniors down from £1m to £600,000 - a much more credible price for a player who had already played for Argentina, who was obviously blessed with genius and whose omission from Cesar Menotti's World Cup squad had caused a major rumpus. This was not a case of Haslam unearthing an unknown gem. The secret was already out.

So the fee Argentinos Juniors wanted for Maradona was, it seems, around 400 per cent of what United eventually had to spend on Sabella - not a cliched case of an excessively parsimonious Yorkshire board who refused t'part with a few notes that they kept hidden inside their flat cap in case World War III was declared. We cannot be entirely sure, because Haslam passed away in 1985 and Maradona inexplicably omitted the incident in his autobiography, but it all has the whiff of a myth. And there's one other thing: even allowing for the transfer climate of the day, why on earth would the world's best young footballer have wanted to play in the English second division, alongside Steve Finnieston, John Cutbush and Mick Speight? Ronaldinho to St Mirren on the other hand…

3) Michael Laudrup (Brondby to Liverpool, 1983)

The fecklessness of those in charge has messed up many a potentially seismic transfer. It's frightening to think how different football's landscape would look had Barcelona's interim board not backed down feebly in the complex Alfredo di Stefano saga of 1953; and it's frightening to think how good an already magnificent Liverpool side would have been had they signed an 18-year-old Michael Laudrup in 1983.

Laudrup had already charmed the cognoscenti, and was in the process of helping Denmark stop England from reaching Euro 84, when Liverpool agreed a fee with Brondby in March 1983. Even though it would have necessitated some kind of tactical reconstruction, the thought of him alongside Ian Rush and Kenny Dalglish watered a lot more than the mouth. Personal terms were agreed, but then Liverpool came back a week later and said they wanted Laudrup for four years rather than three.

Laudrup said no and Liverpool, ludicrously with hindsight, refused to budge on such a relatively piddling matter. It was like dumping someone for leaving the toilet seat up. The deal collapsed and Laudrup instead joined Juventus. It didn't do Liverpool much harm in the short term - they won a treble the following season - but with a player this good, it is impossible not to wonder what might have been.

4) Roy Keane (Nottingham Forest to Blackburn, 1993)

Blackburn's failure to infiltrate the upper echelons of English football for more than a couple of seasons in the 1990s is largely attributed to their inability to strengthen their squad appropriately in the aftermath of winning the Premier League in 1995. This is true up to a point: the likes of Matty Holmes and Graham Fenton were barely names in their own household, and the possibly apocryphal story that Jack Walker vetoed a deal for the Bordeaux pair of Zinedine Zidane and Christophe Dugarry because "we've got Tim Sherwood" hints at a chillingly parochial mentality. Yet their most costly failure came two years earlier, when Blackburn came this close to signing Roy Keane from Nottingham Forest. They may have shared the fiercest mutual enmity, but Keane and Alan Shearer remain the greatest British and Irish players of the Premiership era. You could have had nine complete donkeys alongside them - insert your own Mark Atkins/Ian Pearce/Robbie Slater joke here - but with those two in the side, how much could have gone wrong?

When Keane agreed to join Blackburn on a Friday afternoon, Kenny Dalglish phoned the Ewood Park office to arrange the paperwork, only to find that everybody had gone home. On such gossamer-thin margins did the modern history of English football rest. Keane instead shook hands on a deal and went home to Cork for a celebratory weekend of booze and kebabs. Somewhere in amongst all that came a phone call from Alex Ferguson, who asked Keane to sign nothing until they had met. It was the first time Keane had heard from Ferguson, who was either remarkably blasé or extremely lucky. No matter: Ferguson and the prospect of playing for Manchester United wooed Keane so much that he called off the deal, leaving Dalglish apoplectic. After a long rant, Dalglish concluded that Keane was a "wee bastard". Opposing fans would call Keane a lot worse over the years, but mainly because they know how influential he was. He would have been every bit as influential at Blackburn.

5) Steven Gerrard (Liverpool to Chelsea, 2005)

Many transfers form part of a property chain: if one breaks down, so do the rest. Take Gareth Barry and Xabi Alonso last summer. Or Patrick Vieira. Had Vieira gone to Real Madrid in 2004, Michael Carrick would almost certainly now be an Arsenal player. Everyone knows how frustrating it is not to get the property you had set your heart on, yet sometimes the second option turns out to the best. We may never know whether Steven Gerrard's decision to reject an apparently inevitable move to Chelsea was motivated by simple loyalty of something more sinister, but one thing seems certain: had Chelsea signed Gerrard, they would not also have signed the peerless Michael Essien the same summer.

6) Mick Harford (Luton to Manchester United, 1992)

Given the quality of player managed by Sir Alex Ferguson in the last 25 years, the list of those that got away - Paul Gascoigne, Alan Shearer, Brian Laudrup, Patrick Kluivert, Patrick Vieira, Ronaldinho, Arjen Robben - is pretty terrifying. Yet perhaps the most intriguing is Mick Harford. You heard: Mick Harford.

Yes, Harford was 33 and hadn't scored even 10 league goals for the previous five seasons, but Ferguson's reasoning was sound. United's attempt at passing their way to a first title in 25 years was being lost amid an awful Old Trafford pitch - having scored 19 goals in the last six league games of 1991, they would score just 18 in the next 20 - and Ferguson wanted an alternative option. It was very much a quick fix: a short-term fling with a bit of rough to get United through the spring months.

He discussed a deal with the Luton manager David Pleat but then, perhaps conscious that Harford was not the type of player Manchester United should be seen to buy, pulled out. It's easy to belittle Harford, from a safe distance anyway, but he was no mug: he played for England and came to symbolise the old-school target man every bit as much as Gary Cooper symbolises the strong, silent type. "If I had acted as purposefully as I should have done," said Ferguson in his autobiography, Managing My Life, "we would have won the league." Instead it was their rivals Leeds, who bought an entirely different type of striker for the run-in in Eric Cantona, and walked away with the title.