The Magpies' fourth defeat in a row has raised the question as to whether Benitez should revert back to his 4-5-1 formation, and the Spaniard said he will assess the situation.
Will Hughes opened the scoring for the Hornets before a DeAndre Yedlin own goal on the brink of half-time put the visitors well in control.
And with Watford pushing for a third to put the game out of sight, Andre Gray applied the all-important killer blow just after the hour mark.
Benitez implores Magpies to stay unified
Speaking in his post-match press conference after the game, Benitez said: "We have to realise, the staff, the players, the fans, the media, that the only way for us is to keep working harder and together.
"We have to realise we are a team that has to work hard from now to the end of the season."
And when asked if a lack of confidence has wriggled its way into the United dressing, the 57-year-old said: "We have to realise that it can happen – we lose games.
"We are in the Premier League – it's another level. Everyone needs to know that if you want to improve, we have to work harder and better."
Reverting back to old ways?
Since switching to starting Dwight Gayle and Joselu as a front two after the defeat at Burnley last month, the Magpies fortunes have remained the same - losing a further three games.
"We will analyse how the players are and which are the best for every game," added Benitez, when questioned whether he'd revert back to playing a lone striker.
"There is not just a question of the shape of the team or the formation. It is a question just to understand that we are a team that has to work very, very hard if we want to get results.
"They are working hard but in the second-half when we concede, we were a little bit disorganised and we have to go back to the principles that we were compact and working as a unit.
"That doesn't matter if you are playing with two strikers or one, you are compact enough to defend and attack."