Chris Young: What a difference it makes for Sunderland signings to make an instant impact

They either shine on their debuts and then fade away, take three months before they even begin to make an impact, or simply contribute the sum total of nothing.

Ellis Short - a spectator at the Stadium of Light - has seen plenty of players in all those categories over the last four years.

But Lamine Kone and Wahbi Khazri have bucked that trend. From their very first outing in a red and white shirt, they have oozed quality and capability, and have remained on an upward curve.

Far from struggling to adapt to the pace and power of the Premier League, the pair of imports from France's Ligue 1 have revelled and instantly improved a Sunderland side slipping towards relegation.

That's no mean feat, particularly considering the calibre of teams that Sunderland have faced over the last couple of weeks.

Khazri was understandably huffing and puffing on the hour mark, as his exertions in tracking back doggedly, while providing an attacking threat at the other end, took their toll.

But then the Tunisian international kicked again. That's not purely adrenaline after two previous outings for Sunderland. It's desire to prove his credentials as Premier League player.

The £9million recruit still had the poise to deliver an inch-perfect corner onto the head of Lamine Kone in the final 10 minutes, which the Ivorian powered home.

Like Khazri, Kone will benefit from the next couple of weeks between games, to catch his breath and recover physically from his significant exertions.

But it wasn't just the goal which was impressive about the ex-Lorient man.

Alongside the equally dominant John O'Shea, Kone again showed the physicality and athleticism which has been required in Sunderland's back-line for the last two or three years.

Setting aside early casualty Jan Kirchhoff, the other one of Sunderland's January recruits, Dame N'Doye, deserves some praise too.

N'Doye isn't a right winger by trade, but he tracked back diligently, held the ball up and was happy to run with it. After 70 or so indifferent minutes at Liverpool seven days earlier, he looked far sharper and fitter.

The new boys sparked a performance which - other than the final 15 minutes of the first half - saw Sunderland well on top and fully merit a first Premier League victory over United on home turf since John Mullin's winner in 1997.

Realistically, Sunderland needed to take a scalp of one of the top flight's heavyweights during the run-in if they were to stand a chance of yet again escaping the drop.

Sam Allardyce's men have now done that, and taken four points from a daunting run of three games.

Sunderland will still require four or five wins during the last 12 games if they are to complete their survival mission, but the Black Cats are unquestionably looking a side more capable of achieving that tall order with the new boys in their midst.