Sunderland have had their fair share of howlers in the transfer market over the years by overpaying for players who went on to fail on Wearside.

The likes of Didier Ndong and Jack Rodwell are names that instantly spring to mind and there have been plenty of other examples in the 21st century.

One player the club had a shocker with from a financial perspective was central defender Michael Turner, who joined the Black Cats from Hull in 2009.

There is some controversy over exactly how much Sunderland paid to sign the defender, who put pen to paper on a four-year contract at the Stadium of Light.

The Daily Mail claimed that the fee was £6.5m, whilst The Guardian initially reported that it was in the region of £12m. Giving the club the benefit of the doubt, we will assume that it was the former in this case.

Steve Bruce hailed the Englishman's talent at the time of the move, saying: "I believe that Michael is one of the country's premier central defenders. I have been looking to add size and strength to the back line and Michael fits the bill perfectly in that respect, as well as being an excellent technical footballer."

Turner enjoyed a solid first season on Wearside as he started 29 Premier League matches and averaged a WhoScored rating of 7.09 for the Black Cats, which placed him 8th in the squad.

However, he then struggled to keep up with the high standard that he set as he played 39 top-flight matches and failed to average a score higher than 6.89 in the following two campaigns.

In terms of WhoScored ratings, he ranked 16th and ninth in his final two seasons at the Stadium of Light in 2010/11 and 2011/12 respectively.

These statistics suggest that he was far from being one of the club's best players during his three-year spell and the Black Cats opted to cash in on him in the summer of 2012 after his failure to kick on from his debut campaign.

Sunderland sold him to fellow Premier League side Norwich City for a reported fee in the region of £1.5m, taking a sizeable hit on the initial £6.5m they paid for him.

Turner was 28 at the time of the move and still had plenty of years left to give, which suggests that the club did not feel he was at the required level for them anymore.

Therefore, Bruce had a shocker with the central defender as it hurt Sunderland from a financial perspective. They spent a net amount of £5m on him for one good year of service and two average, at best, seasons. That certainly suggests that the signing was not a success from an on-pitch or off-pitch point of view.