Nicolas Lombaerts has failed a medical with Sunderland, according to reports from both Sky Sports and Sunderland Echo.
Speculation regarding the failure of a medical first emerged in Italy last night, but the news has since been confirmed by reliable sources.
It is believed that Lombaerts, currently at Zenit St Petersburg in Russia, had agreed personal terms with the club, despite reports suggesting disagreements regarding the player's wages, whilst Sunderland had also reached a deal with the defender's club over a transfer fee - one in the region of £5 million.
However, the Black Cats will now have to look at other targets who they believe can strengthen their back line after this deal collapsed.
Other targets?
Sunderland manager Dick Advocaat was initially interested in Celtic man Virgil van Dijk, a fellow Dutchman, but with the Scottish Champions adamant that he will not be sold, the club have already been forced to move on.
Rumours have linked Cameroon international and Marseille defender Nicolas Nkoulou with a move to Wearside too, but Newcastle United and Aston Villa are also said to be in the race for his signature, meaning he could be a difficult target to capture.
Yet, Sunderland Echo understands that the club's new defensive targets have already been idenitified.
Not strong enough yet
The interest in Lombaerts showed that Advocaat does not yet believe his back line is good enough for improvements to be shown in the forthcoming season.
Sunderland have already signed Adam Matthews from Celtic for £2 million this summer, as well as Sebastian Coates for £4 million from Liverpool, both centre-backs who will strengthen a defence that was horrific at times last season as the Black Cats just survived the drop.
However, although Wes Brown has just signed an extension on his contract last month, Advocaat is keen to recruit more options at the back with Santiago Vergini set to leave the club still.