The Black Cats scored a goal in each half via Jobe Bellingham and Wilson Isidor, and if not for a couple of top saves by Jamie Cumming, the scoreline could’ve been more.
Here are the key talking points from the clash at the Stadium of Light.
Read our player ratings from the Stadium of Light here
Time for a change of shape?
United are now seven games without a win, a run of results which has seen five draws bookended by defeats.
The brilliant start to the season meant the buffer between the clubs at the bottom of the table was a healthy one in the opening weeks of the season, but now stands at three points.
Added to the run of form is a worrying injury list out wide, with Siriki Dembele, Kyle Edwards, Matt Phillips and Przemyslaw Placheta all sidelined.
There had been murmurs of a change in shape for the trip to Sunderland, and at half-time it proved to be the case.
Des Buckingham introduced Greg Leigh for Idris El Mizouni as the U’s switched to a 3-5-2 set-up.
Peter Kioso and Leigh provided the width from wing back, and the latter in particular was a useful outlet in the second half.
Whether the fitness and form situations lead to Buckingham sticking with the back three at home to Swansea City next weekend will be interesting.
A dose of realism
The result at the Stadium of Light also needs placing into context a little bit.
Sunderland lead the Championship by five points and have got some phenomenal talent in their ranks.
Jobe Bellingham and Chris Rigg were wonderful in midfield, while the Black Cats front three all provided a killer threat in attack.
Sunderland stroked the ball around with purpose, were incisive in their passing, and won back possession very quickly. They’re the best team United have faced, of that there is no doubt.
Their two goals exemplified that. A lovely cross by right back Trai Hume was thundered in by Bellingham, while the technique shown by Wilson Isidor as he watched the ball drop over his shoulder before volleying in was marvellous.
Mark Harris moves to wide role
In the first half, Harris played wide, with Dane Scarlett up front. Harris was initially on the left, but soon switched with Tyler Goodrham.
It was a tough afternoon for Harris, who spent more time tracking back than getting forward.
When the U’s switched to a 3-5-2 in the second half, Harris partnered Scarlett up front.
Against most other teams in the division, there will be more opportunities to attack from a wide position for Harris, so it’s hard to tell how successful the experiment was in truth.