The visitors offered little in attack and their constant time-wasting left a sour taste in the mouth for many Boro fans, but there can be no excuses after another performance which echoed much of what has been wrong with Aitor Karanka's side this season.
With a daunting run including games against Arsenal, Manchester City, Chelsea and Leicester City in the coming weeks, Middlesbrough needed a win - and it is worryingly simple to pinpoint why the result did not come.
Negredo struggles as Stuani offers no supply
When Boro announced the ambitious signing of Alvaro Negredo over the summer, it seemed obvious what their game plan would be - have their wingers put crosses into the box and back 'the Beast' to get on the end of them.
However, the system that has been deployed since the departure of Albert Adomah has been lopsided and largely ineffective. George Friend and Stewart Downing have provided some threat down the left, but Boro's right flank has been a constant source of frustration.
However, it constantly seems as though he has a net negative influence on Boro's attack. With no obvious pace or skill, he rarely beats his man and his crossing has been poor all season. Unless he is to step up and hit the goalscoring trail as he did in the first half of last season, he is a player Middlesbrough cannot afford to keep starting.
Traore is the risk Karanka must take
It is clear when watching Adama Traore that he is not the finished article. He is only 20 years old, and to expect him to have the positional awareness, tactical nous and composure of a player ten years his senior would be unreasonable.
His dribbling is at times erratic, his final product inconsistent. But he offers a spark which, at the moment, simply isn't there from the rest of Boro's side.
For all of Downing's crossing ability, Adam Forshaw's tidy passing and Gaston Ramirez' intermittent inspiration, there is no member of Boro's starting eleven to scare an opposition defender.
In 20 minutes in the second half, Traore took the ball past more players than the rest of the team seemed to manage in 90. His pace stretched the Watford back three/five and, while his crossing was not perfect, it was a marked improvement from his contribution against Spurs.
At the moment, Middlesbrough's conservative approach is not working. They are in a relegation fight, without any doubt. Traore can be the man to pull them clear.
Further investment needed in January
It is becoming increasingly clear that Boro do not have the strength in depth needed to hurt teams for extended periods of Premier League games.
Traore aside, Boro's bench rarely inspires. Jordan Rhodes and David Nugent were a fearsome striking duo in the Championship, but they will not overly worry top-flight defences more concerned about clashes with Sergio Aguero, Zlatan Ibrahimovic and Diego Costa.
Viktor Fischer has impressed in fits and starts but Karanka couldn't bring him on against Watford as he was essentially forced to replace the erratic Antonio Barragan, who could easily have had three yellow cards.
Middlesbrough arguably need two more attacking players. Promising youngsters and ageing mercenaries will not do - Boro need a Fuchs or Ramirez-esque mid-season spark from a player in their prime years, and to find this in January will take a significant financial gamble.
Loan players may be an option in the short term, but Boro cannot afford to go straight back down after seven years of toil and tedium to get them back up. The psychological and economic effects on the club would be disastrous.
It is difficult to see where points will come from until the fixtures start to soften slightly in January, and by then they may well find themselves dug into the bottom three. Boro need to roll the dice.