The French defender moved to the Black Cats from Premier League rivals Tottenham last month.
The 29-year-old centre-back struggled for playing time at Spurs last season - he could make just 11 appearances in the league - but he is expected to play a key role for Sunderland in the Premier League this term.
However, Kaboul has started his Sunderland career on a disappointing note, as Dick Advocaat’s side have lost both of their Premier League games this season.
Former Arsenal attacker Merson has criticised Sunderland's decision to sign Kaboul.
“I watched their opening defeat against Leicester and that team looks like it could struggle to me,” the 47-year-old wrote in The Daily Star.
“They could be fun to watch because they can’t defend so they might as well have a go at teams. But they’ve bought badly. Is Younes Kaboul a relegation battle centre-half? Not for me.”
Merson made his comments after Sunderland’s 4-2 defeat to Leicester City away from home at the King Power Stadium on the opening weekend of the season.
In that match, Kaboul took one shot, had a pass accuracy of 74%, put in one cross, won 100% of the tackles and 70% of the headers, and made one interception, four clearances and two blocks.
The Frenchman was part of the Sunderland team that lost 3-1 at home to Norwich City this weekend.
During his 90 minutes on the pitch at the Stadium of Light, Kaboul took one shot, had a pass accuracy of 60%, won 57% of the tackles and 50% of the headers, and made four interceptions, nine clearances and three blocks.