The 29-year-old loan signing lags behind the rest of his new squad in terms of fitness and sharpness after spending the last six months at Saudi club Al-Hilal.
The 6ft 5ins centre-half, previously of top French sides Lens and Rennes, has played 18 games since his move to the Arabian side in the summer.
But their league is massively less demanding than the English Premier League, and he has been working on his fitness since arriving on Wearside last week on a loan deal.
It keeps him at the Stadium of Light until the end of the season.
Martin O’Neill: “It’s fair to say that Kader’s a little bit behind the rest of the lads in terms of his fitness levels, but we’re looking to address that, and we’ll step that side of things up this week.
“Whenever a loan signing comes in from abroad, part of the deal is that there has to be an option at the end of the loan deal for a permanent signing, and that’s the case with Kader.
“So we’ll see how it goes.
“He’s got a great physique and presence at the back, he’s got what it takes to do a job at this level, and we’ll just see how he comes on during his time here in the remainder of this season.
“Physically, he adds a different dimension to the side and he demonstrated in France over a number of seasons that he is a quality player.
“This is an opportunity for him.
“But the main thing for the moment is that he gives us an option in a position where we’ve been really stretched of late and once he’s fully fit, he’ll be pushing for a start and giving us some competition for places.”