Sunderland are currently in the League One play-off places, seeking a return to the Championship at the fourth time of asking.

The Black Cats suffered back-to-back relegations from the Premier League and Championship in 2016-17 and 2017-18 respectively, but having maintained top-flight status for nine seasons prior, have spent a fair amount of money on players over the years.

Some have been more successful than others, but here are the three times Sunderland were well and truly ripped off in the transfer market.

Didier N'Dong

Signed for a reported record fee of £13.6 million pounds, Didier N'Dong joined Sunderland from Lorient in 2016 and is undoubtedly the biggest rip off The Black Cats have shelled out on.

The Gabonese midfielder made 54 appearances for Sunderland in a side that suffered relegation from the top-flight and second-tier.

When Sunderland returned to pre-season after their relegation to League One, the midfielder reportedly went awol - leaving on a free transfer just two years after his record signing.

Not the most shrewd signing the club have ever made.

Papy Djilobodji

A similar mistake was made when Sunderland signed Papy Djilobodji from Chelsea.

The Senegalese defensive player signed for The Black Cats for a reported fee of £8 million pounds - but only made 24 appearances for the club.

Like N'Dong, Djilobodji would also go on to leave the club for free just two years after joining them, with the player reportedly not returning for pre-season training until September in 2018.

This was conduct that saw Djilobodji's contract terminated - like N'Dong - just two years after his multi-million pound signing.

Ricardo Alvarez

Sunderland initially signed Ricardo Alvarez on loan from Inter Milan in 2014, but it was when that loan spell ended that the problems began.

Having made 13 appearances league appearances for The Black Cats, Sunderland tried to get out of the deal to sign him permanently the following summer for a reported fee of £9 million.

Sunderland's argument was that the Argentine's knee injury had rendered the agreement invalid, but the Court of Arbitration for Sport (CAS) later ruled that they had to pay Inter Milan the fee.

CAS also ruled that Sunderland had to pay 4.7 million to Alvarez himself in loss of earnings - an expensive price to pay for a player that never played for the club again after his initial loan spell.