The Black Cats are suing Ishtiaq Rehman over the deal that sparked one of the lengthiest and most controversial legal wrangles in the club’s history.

It’s understood that the action predates the current ownership, who took over the club in May last year.

Here, we look at where Rehman – reported to be facing a staggering £13million claim – fits into the saga, and why it continues to hang over the club to this day…..

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Former Sunderland forward Ricky Alvarez

THE DEAL

Sunderland had endured a mixed summer in the transfer market after Gus Poyet had looked to build on the exhilarating end to the previous season.

Attempts to land Fabio Borini after a successful loan had failed, and though Jack Rodwell was at the time seen as a marquee signing, the Black Cats went into deadline day in need of reinforcements.

Sebastian Coates joined from Liverpool, and Alvarez joined from Inter Milan.

Gus Poyet said the Argentinian would be ‘exciting to watch’.

"He is technically gifted and can do things with the ball that the rest maybe cannot with that last pass, assist or option,” he said.

"Sometimes when a team drops deep it becomes difficult to break them down but he has the ability to break those lines and give us something special.

Court documents subsequently showed that the agreement in place was that should Sunderland secure their Premier League status for the following season, the transfer would automatically become permanent, for a sum of €10.5 million, staggered over four payments.

Should they be relegated, Alvarez would return to Inter Milan.

Crucially, the deal also included a clause relating to the chronic patellar tendonitis Alvarez suffered in his left knee. The clause specified that should the problem ‘accelerate’ to the point where he could not perform as a professional in the Premier League, Sunderland would not be obliged to adhere to the agreement should they avoid relegation.

THE INJURY ISSUES

Alvarez played three games before suffering the injury that would come to define the saga.

He was a second-half substitute in a 0-0 draw with Swansea City, but suffered a knee problem that would keep him out of action until December.

Crucially, the injury was to his right knee.

Alvarez went on to make 17 appearances during the season, including scoring his first goal against Fulham in the FA Cup, but the issue with the right knee persisted (despite surgery following the initial issue) and he made his final appearance of the season in a 4-0 defeat to Aston Villa in March.

Alvarez was taken off at half time in what was Gus Poyet’s final game as manager.

At this stage, court documents showed that a debate between the two clubs began as to whether the player should undergo further surgery.

Sunderland wanted to pursue this option, but Inter Milan informed them in May that they did not consent.

THE LEGAL ACTION

Sunderland were still fighting relegation at this stage but the club informed Inter Milan that regardless of their fate, they believed the agreement was invalid.

The argument was presented on two fronts:

The delay and eventual decision over dealing with the injury in March was a breach of the agreement between the two clubs The right knee issue Alvarez was suffering with was an indirect consequence of the left knee issue, and therefore under the terms of the agreement, Sunderland would not obliged to fulfil the permanent clause of the deal

Inter rejected this and when survival was secured, they emailed the Black Cats a congratulary message, reminding them of the terms of the deal.

The case was first heard in July 2015 by the FIFA Players’ Status Committee.

The ruling was in favour of Inter Milan, ultimately deciding that Sunderland were to pay the first installment of the agreed fee, which was €2.5 million.

In the case, Sunderland argued that they had been unaware of the fact that Alvarez had undergone surgery on his right knee in 2012.

In their ruling, the Bureau stated that they believed the Black Cats had an awareness of the player’s injury history and therefore could have extended the scope of the clause to involve both knees, or indeed the player’s fitness generally.

With regards to the 2012 surgery, they ruled that Inter Milan were not at fault. By the time the ruling was delivered, Alvarez had signed and featured for Sampdoria in Serie A, which was used to argue that the player was indeed fit to play professional football.

Sunderland also lost their claim that they should be entitled to remuneration for the time Alvarez had been injured during the loan spell, which they judged to be 63%.

THE NEXT RULING

The case rumbled on and was settled in the Court of Arbitration for Sport in 2017.

The court ruled again that Inter were not at fault over the contentious issue regarding that surgery in 2012. They stated that Sunderland had identified a potential issue in the right knee during the medical, a concern that they ultimately did not act upon.

The Black Cats had previously argued they had been misled by the player around this issue during the process. The court ruled that they had been unable to prove this claim.

This appears to be the central tenent of the current case as reported by The Sun, who claim that former club doctor Rehman is facing a £13 million claim for not properly relaying the severity of the issue in the right knee to the hierarchy.

Sunderland were ordered to pay the transfer fee in full, on the payment schedule initially agreed.

FURTHER COSTS

The case did not end there for Sunderland.

Alvarez spent the best part of three seasons with Sampdoria, before moving to Mexican side Atlas.

The Black Cats were stung by a further ruling from the Court of Arbitration for Sport, who ruled that Velez Sarsfield, the Argentinian side where Alvarez began his senior career, were owed €362,500.

This was due to FIFA’s solidarity mechanism, designed to compensate clubs for their development of players.

Sunderland could lose yet more on the deal, with Alvarez himself lodging a case with the Court of Arbitration of Sport that was heard at the end of August.

This relates to his alleged loss of earnings while he was a free agent for the first half of the season before he signed for Sampdoria.

The results of the case are not yet known.

It is, without question, one of the most expensive transfers in Sunderland’s history, for a player who utimately featured just 17 times for the club.