For Everton, it has always been the great 'what if?'. For Liverpool, it meant one of their greatest teams went unfulfilled. The likes of Wimbledon, Coventry City, Oxford United and Luton Town were left to lament missing out on rare opportunities to play in continental competition.
Between 1985 and 1991, both Liverpool and Everton had sides that can be considered among the finest in their histories, while many other English clubs were enjoying some of their greatest days.
Howard Kendall's Everton had won the league and the Cup Winners' Cup in 1985, with that domestic title the first of two in three years. Liverpool, meanwhile, secured their only domestic double before producing one of their most wondrous teams in 1987-88. That side was nevertheless beaten in the 1988 FA Cup final at Wembley by Wimbledon, who followed Oxford in 1986, Coventry (1987) and Luton (1988) as shock winners of a domestic cup.
The reason none got the opportunity to test their qualities overseas was one of the worst days European football has seen. English clubs were banned from continental competition for five years after a decade of crowd trouble culminated in the disaster at Heysel and the deaths of 39 fans.
For reasons beyond the obviously tragic, that day in Brussels marked a clear line in football's history. Before it, English sides had claimed seven European Cups in nine years and Liverpool had lost the 1985 final. After it, the competition saw its most open and varied era since the late 1960s.
In 1985-86, Steaua Bucharest became the first side from east of Germany to win the trophy. Porto then lifted Portugal's first in 26 years before PSV claimed the Netherlands' first in 15.
The immediate assumption is that the English clubs left a vacuum, and that they could have anticipated a few more continental victories over that period. It leads to those big questions: Would Liverpool now have the European Cups to rival Milan? Would Everton have one? Would Arsenal have claimed another trophy? How would the continent have coped with the Crazy Gang?
A deeper look begins to indicate that England's power had already waned. For one, the European Cup's most powerful country between Aston Villa's win in 1982 and Liverpool's loss in 1985 was Italy, with one victory and two finalists. Further emphasising that shift, Liverpool had lost Graeme Souness to Sampdoria in 1984.
Although English clubs claimed three victories in the UEFA Cup and Cup Winners' Cup, the nationalities of the finalists from all the competitions combined in that period pointed to th coming variety. The 18 from 1982 to 1985 read:
4 - Italy, England
2 - Portugal, Belgium, Spain
1 - Germany, Scotland, Hungary, Austria
In that context, a spread of European champions from leagues as diverse as Romania, Portugal and the Netherlands isn't outlandish. In addition, the open nature of seeding system at the time saw some competitors of the highest quality knocked out of the elite trophy early on. Among the most famous were Diego Maradona's Napoli, the Real Madrid 'Quinta del Buitre' team and a Bayern Munich side that provided the core of West Germany's 1990 World Cup winners. Such is the often random nature of knockout football.
Of course, the presence of English sides in the competitions would have caused further ripples in the pool, and there's no accounting for how that would have altered the course of the campaigns or how those teams would have adjusted to the transfer market or the tactical quantum leaps made by Arrigo Sacchi's Milan. In order to attempt to speculate on how specific tournaments might have gone, all we can do is analyse the available evidence.
European Cup final: Steaua Buchaest 0-0 Barcelona (Steaua won 2-0 on penalties)
UEFA Cup final: Real Madrid 5-3 Koln agg
Cup Winners' Cup final: Dynamo Kyiv 3-0 Atletico Madrid
English qualifiers: European Cup - Everton; Cup Winners' Cup - Manchester United; UEFA Cup - Liverpool, Tottenham, Southampton, Chelsea, Norwich City.
Probably England's best chance of the whole period of winning another European Cup. As such, Everton can feel aggrieved. The previous season, Kendall's wonderfully balanced side had won two trophies. They scored 88 goals in 42 league games and collected 90 points - some of the finest totals in English history.
They carried that form into the 1985-86 campaign, hitting 87 goals and accumulating 86 points - but a resurgent Liverpool had just a little too much in the league. The all-action Andy Gray had been replaced up front by poacher Gary Lineker, and it is likely that the English forward's subtlety would have better suited the tactical minimalism of mid-80s European football. Given the premium on goalscoring opportunities, his predatory instincts could well have been perfect.
Certainly, the goalless final was Lineker's kind of game - and it is telling that Barcelona signed him that summer. And while that staid showpiece may not have been the fairest reflection of a Steaua Bucharest admired by the likes of Arie Haan for their glorious rhythm, they were one of very few teams in that European Cup at the right point of a cycle.
That wasn't the case with Everton, and it's difficult not to think that they would have been strongly competitive - if not favourites. In the 1985-86 Cup Winners' Cup, it seems likely that Ron Atkinson's Manchester United would have been a touch too naive for the technical Dynamo Kyiv. Double-winning Liverpool, however, might well have troubled Real Madrid in the UEFA Cup.
European Cup final: FC Porto 2-1 Bayern Munich
UEFA Cup final: IFK Gothenburg 2-1 Dundee United agg
Cup Winners' Cup final: Ajax 1-0 Lokomotive Leipzig
English qualifiers: European Cup - Liverpool; Cup Winners' Cup - Everton; UEFA Cup: West Ham United, Manchester United, Sheffield Wednesday, Chelsea, Oxford United
The key question is whether Liverpool's experience would have told over the exuberance of some bright young sides. The key fact, however, appears to be that this was still an Anfield outfit that badly required revitalising. That was proved by the manner in which Kenny Dalglish made extensive changes in the summer of 1987, just a year after their domestic double.
In effect, Liverpool's old resilience had brought that new feat. After a mediocre start to the 1985-86 season (by their standards), they found enough focus to win ten of the last 11 games.
Whether that would have been enough in Europe is another matter. The spark seemed to have gone. Porto had plenty of it, illustrated by the manner in which they eliminated one of the strongest sides of the decade, Dynamo Kyiv, and then beat burgeoning Bayern Munich in the final. Players such as Paolo Futre and Rabah Madjer added effervescence to a strong defensive base. Any clash would have been close, especially with Emilio Butragueno's Real also in the mix.
It's likely that Everton would have encountered a similarly even game in the Cup Winners' Cup, with an excellent Ajax side boosted by the rises to stardom of Marco van Basten and Frank Rijkaard, but fourth-placed Arsenal would have fancied their chances in the UEFA Cup against Sven Goran-Eriksson's surprising champions at Gothenburg. Given that none of England's other entrants finished higher than 11th in the league, any other impact would probably have been minimal.
European Cup final: PSV Eindhoven 0-0 Benfica (PSV win 6-5 on penalties)
UEFA Cup final: Bayer Leverkusen 3-3 Espanyol agg (Leverkusen win 3-2 on penalties)
Cup Winners' Cup final: Mechelen 1-0 Ajax
English qualifiers: European Cup - Everton; Cup Winners' Cup - Coventry City; UEFA Cup - Liverpool, Tottenham Hotspur, Norwich City, Arsenal
An era had ended at Goodison with Kendall's departure for Athletic Bilbao in the summer of 1987, and the effect was seen in their immediate drop to fourth in the league, 20 points behind Liverpool. Although Villa overcame similar issues to win the European Cup in 1982, that was at a different time. It seems unlikely Everton would have had the edge to overcome Guus Hiddink's tactical pragmatism with PSV - let alone the freescoring Real Madrid and Napoli.
In England, Liverpool were in similarly freewheeling form and would have been favourites in an open UEFA Cup won by Bayer Leverkusen. Tenth-placed Coventry, meanwhile, may have had an outside chance of a Cup Winners' Cup run. Ajax would have been a tough challenge, but not so much the Mechelen side that beat the Dutch outfit in a one-off final.
European Cup final: AC Milan 4-0 Steaua Bucharest
UEFA Cup final: Napoli 5-4 VfB Stuttgart agg
Cup Winners' Cup final: Barcelona 2-0 Sampdoria
English qualifiers: European Cup - Liverpool; Cup Winners' Cup - Wimbledon; UEFA Cup - Manchester United, Everton, QPR, Luton Town
One of the great head-to-heads Europe never got to see? It is certainly a pity that a genuinely brilliant Liverpool never got to pit their wits against Sacchi's Milan. Dalglish's exhilarating side had won the 1987-88 title with one of the highest points records, and one of the best scoring ratios, of modern times. That had come about thanks to the glorious movement of John Barnes, Peter Beardsley, Ray Houghton and John Aldridge. Liverpool were effectively playing a fluid 4-2-3-1 more than ten years before it became fashionable.
The only problem was that Milan had already made an even greater leap. Sacchi's approach altered European football on the pitch, while Silvio Berlusconi's plans did the same off it. Not only did those changes set up Serie A's decade-long dominance, they explained why it took English sides so long to catch up after missing the early years of these innovations.
The UEFA Cup entrants, who finished no higher than eighth in the league that season, would have struggled to cope with either Napoli or Juventus. In the Cup Winners' Cup, Johan Cruyff's Barcelona were better equipped than most to simply play around Wimbledon. Milan, of course, did that to so many others. It is probable they would have had too much for Liverpool, even if the Merseysiders' dynamism would have made it close.
European Cup final: AC Milan 1-0 Benfica
UEFA Cup final: Juventus 3-1 Fiorentina agg
Cup Winners' Cup final: Sampdoria 2-0 Anderlecht
English qualifiers: European Cup - Arsenal; Cup Winners' Cup - Liverpool; UEFA Cup - Norwich City, Derby County, Tottenham Hotspur, Nottingham Forest
George Graham's pragmatic Arsenal, who had dipped to fourth, would not have been able to cope with a Milan side at their peak. In general, Serie A had probably moved too far ahead for either Sampdoria or Juventus to be troubled in the other competitions.
European Cup final: Red Star Belgrade 0-0 Marseille (Red Star win 5-3 on penalties)
UEFA Cup final: Internazionale 2-1 Roma agg
Cup Winners' Cup final: Manchester United 2-1 Barcelona
English qualifiers: European Cup - Liverpool; UEFA Cup - Tottenham Hotspur, Arsenal
Milan's controversial quarter-final exit may have opened up the European Cup, but Dalglish's shock resignation in February 1991 would have closed it off again for Liverpool. It is of course possible that continental football might have kept his fire alive, but he was struggling to cope with the trauma of the Hillsborough disaster.
Marseille had taken on Milan's free-spending approach - and that still wasn't enough to beat Red Star Belgrade. Given the changes across the continent, Manchester United's Cup Winners' Cup win would probably have remained the one-off English win of that time.