The former Tottenham man is a defender out of form and fitness. Will he prove a good signing?
Make no mistake, Dick Advocaat is a brilliant manager. And the fact the Sunderland boss has identified just how badly his side need to strengthen their back four is a credit to his transfer nous.
In his prime, Kaboul was more than capable of doing a job for a side like Sunderland.
That was a long time ago. The man the Black Cats have now splashed out £3m (fee quoted by the Daily Mail) on is one without much match practice or fitness, one horribly out of form and one that was even a disruptive influence on his team-mates last season.
Indeed, while the Tottenham defender went from club captain to out-of-favour centre-back frighteningly quickly, he also ended up breaking into on-pitch arguments with Jan Vertonghen.
Sunderland's big problem, of course, is a lack of options and a need to get things done quickly.
But the Kaboul signing smacks of trying to get things done a little too quickly. At White Hart Lane, the Frenchman struggled not just against the top sides but teams all over the Premier League. A little like the John O'Sheas and Wes Browns of this world, there is a real danger Kaboul will never return to his best and may just continue to struggle at the Stadium of Light.
Advocaat will no doubt hope that isn't the case, while he did work wonders with the likes of Sebastian Coates during his short stint with the Black Cats last term.
In signing Kaboul from Spurs, though, Sunderland have taken a huge relegation gamble.