Despite a bright start, the Black Cats fell a goal down in the 17th minute when defender Christian Kabesle headed home a corner.
Sunderland were then undone by another set-piece, as Ryan Porteous headed in another corner midway through the second half.
The hosts did manage to pull a goal back immediately when Luke O’Nien converted from close range in the 70th minute, before Patrick Roberts scored an excellent equaliser in stoppage-time.
Here’s how Phil Smith rated the Sunderland players against Watford:
1. Anthony Patterson - 6
Little he could do about either goal and the frustration was that he was barely tested other than from those two set pieces. Distribution was steady in the main. 6 Photo: Martin Swinney
2. Lynden Gooch - 6
Quiet during the first half but got into some aggressive positions late on and that helped his side build pressure and create space for their forwards. 6 Photo: Frank Reid
3. Trai Hume - 5
Not at his most precise in possession and was part of a patched-up defence left frustrated from set-piece situations. This was the afternoon that injuries at the back caught up with Mowbray’s side. 5 Photo: Frank Reid
4. Luke O’Nien - 5
Played a sloppy pass in the build up to the first goal but kept trying to be aggressive in setting his team going on the ball. Dealt OK with the dangerous Davis for the most part. 5 Photo: Frank Reid