The former Tottenham Hotspur defender looks to be carrying on where he left off at White Hart Lane.
Fans on Wearside will no doubt hope the Frenchman can improve with game time and fitness - two things he didn't have at White Hart Lane last term.
If not, though, Sunderland supporters are in for a long season indeed. Considering Kaboul's woeful form at Spurs last campaign, it was always a risk bringing the 29-year-old in at a side that only narrowly escaped relegation last season.
And the centre-back looked as though he was simply carrying on where he left off at Tottenham as the Black Cats lost 4-2 to Leicester City on Saturday afternoon.
Sunderland were 3-0 down in the first half after a shambolic defensive performance and it was far from the ideal season opener for Dick Advocaat as Claudio Ranieri got an early chance to hit back at his critics at Leicester City.
And Sunderland fans were distraught on Twitter that they were seeing the same Kaboul who went from Tottenham captain to first-team outcast last campaign. Here's how they reacted on Twitter to the 29-year-old's disastrous debut...
Haha I was saying it had to be Kaboul and Coates to start! Christ what was I thinking! #safc— Andrew Robertson (@scatch21) August 8, 2015
Any chance of a refund for Sebastian 'I have a fridge on my back' Coates & Younnes 'I just look weird' Kaboul? #Safc— Bradley Hudson (@bradsafc1093) August 8, 2015
Seems safe to say the Kaboul experiment isn't working. #SAFC— Robert M. Cook II (@RMCookII) August 8, 2015
I've played better in a Sunderland shirt than Kaboul #SAFC— Alex Dismore (@Dizzydismore) August 8, 2015
Replacing John O'Shea with Younes Kaboul is like swapping your beer for a pint of piss #SAFC— Ste Linsley (@SteLinsley) August 8, 2015
And Spurs fans had plenty to say too...
Quote Merson , Kaboul had a shocker , didn't know what day it was !! How much #3 mill , good business levy , now go and spend it #COYS— Nigel Richards (@Welshyid1966) August 8, 2015