An arbitration tribunal begins a two-day hearing on Monday to examine the decision by an independent committee set up by the Premier League not to dock West Ham points for breaching rules governing the ownership of players.
The Hammers found themselves in trouble after entering into agreements with a third party when signing Argentine duo Carlos Tevez and Javier Mascherano from Brazilian club Corinthians in August 2006.
Following a hearing into the case in April, the London club were fined £5.5m but escaped a points penalty and were allowed to retain the services of striker Tevez, much to the anger and bemusement of some top-flight clubs.
Midfielder Mascherano had already left the club by then, joining Liverpool in February, but Tevez went on to play a key role in West Ham's successful battle to avoid relegation.
PREMIER LEAGUE'S BOTTOM SIX
Among the clubs upset at the leniency of the punishment handed out to the Hammers were Sheffield United, who were subsequently relegated from the Premier League on the final day of the season following a 2-1 defeat by Wigan.
The Blades argue West Ham should have been docked points, which would have affected the club's chances of beating the drop and possibly kept the Blades in the Premier League.
The Yorkshire club hope the arbitration tribunal will find in their favour but it is a complex case.
Here, BBC Sport analyses the key elements of the row.
DO SHEFFIELD UNITED HAVE A CASE?
The Premier League does not think so and has stated its case on numerous occasions.
The issue is this: when Tevez and Mascherano were registered as players, West Ham failed to disclose that they had entered into an agreement with third-party companies.
That was against Premier League rules and led to the formation of an independent commission to decide what punishment the Hammers should face.
It concluded that docking points from the London club would be disproportionate to the "crime" they had committed.
Such a deduction so late in the season, it argued, might consign the club to relegation - and that would be unfair on the Hammers players and fans who were in no way to blame for the situation.
However, the decision to only fine the Hammers upset a number of other clubs and led to talk of possible legal action against the Premier League.
That prompted the Premier League to issue a letter to all 20 top-flight clubs stating that any action "would fly in the face of the disciplinary structure that the clubs themselves created" and "would, as a matter of law, be bound to fail".
A subsequent letter from the Premier League also insisted Tevez was clear to play in the final few games of the season after West Ham gave assurances they had terminated the problematic third-party agreement.
WHAT IS THE JOB OF THE ARBITRATION TRIBUNAL?
The Premier League says the arbitration tribunal will decide whether they acted correctly.
It will do that by reviewing "the processes followed by the Premier League from when the rule breach first came to our attention in January of this year".
However, there is another issue. There are also concerns whether West Ham ended their third-party agreement to the satisfaction of all involved.
Reports suggest Kia Joorabchian, who owns one of the third-party companies and who was influential in the duo's arrival at West Ham, could give evidence at the hearing.
Just what the Iranian-born businessman might say is open to speculation but it could shed more light on the deals involving both Tevez and Mascherano.
However, according to the Premier League, he is unlikely to appear and if he is unhappy with the manner and the way the third-party agreement was ended then it is up to him to take it up with the Hammers.
The Premier League say they saw all the documentation bringing the third-party issue to a close and that this is not an issue.
WHO IS ON THE ARBITRATION PANEL?
The three-man panel is made up of Sir Philip Otton, a retired judge of the Court of Appeal, David Pannick QC and Nicholas Rendell.
Sir Philip has chaired high-profile disputes in the business world as well as numerous football matters.
He headed the Premier League disciplinary commission looking into the tapping-up row against Chelsea, former Arsenal defender Ashley Cole, who is now at Stamford Bridge, and Blues boss Jose Mourinho.
All three parties were fined after they were ruled to have breached Premier League rules by meeting at a London restaurant without the knowledge of Cole's then club Arsenal.
Pannick defended Cole in that case and will be Sheffield United's representative on the tribunal. Rendell will act for the Premier League.
WHAT COULD HAPPEN?
If the arbitration tribunal finds in favour of the Premier League, then Sheffield United will have to accept that they will be playing their football in the Championship next season.
But if it rules that West Ham should have been docked points, then the Premier League will be left in a difficult position.
Does it relegate the Hammers and reinstate the Blades? If so, the Upton Park outfit could start their own legal action and prolong matters even further.
The Premier League has insisted all along that all 20 clubs agreed to the disciplinary system in place and that they had to abide by any decision.
It could refuse to overturn the decision, even if the arbitration tribunal rules in favour of Sheffield United. If that happens, the Blades are likely to take their case to the European Commission.
The Blades have suggested that both teams should remain in the top flight in a 21-club Premier League. But whether the other clubs will be willing to give up more of their share of the £2.1bn pot might be an issue.
Plus, there would be a problem regarding the fixtures. The top two tiers of English football would be left with an odd number of teams, which would mean one team in each division having to go without a game during each round of matches.
Another solution could result in the Premier League providing compensation to the Blades. This could be the quickest and most acceptable way to end the dispute.
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