Following a derby defeat to City and a Europa League loss to Feyenoord, Mourinho and United have endured a rough eight days.
It is the first time that the Portuguese manager has lost three consecutive games in a season since February 2002 when he was Porto boss.
But the self proclaimed "Special One" is looking anything but at present, having lost eleven of his last 21 league games in charge of Chelsea and now United.
Mourinho made five changes to his starting line-up from the trip to Rotterdam, with Wayne Rooney and Zlatan Ibrahimovic restored to the side but we were disorganised and ineffective, particularly in the first half.
The United boss looked unhappy with the hosts opening goal- feeling, rightly, that Anthony Martial was fouled by Miguel Britos, but he surely needs to focus on our own failings as we slipped six points behind early Premier League pacesetters City, albeit only five games into the season.
Wayne Rooney, Zlatan Ibrahimovic and £89 million man Paul Pogba all struggled to make an impact on the match and at the back United failed to cope with Watford's energetic pressing and the quality of crosses from wing-backs Janmaat and Jose Holebas.
United did have some hope in the second half when Watford's high pressing tactics looked to have taken the energy out of them in an improved showing from the visitors, but the visitors responded to record back to back wins and their first at home.
Pogba did have United's best effort in the first half when he hit the bar with a 25 yarder that was unlucky not to go in.
But his qualities as an attacking midfield playmaker were wasted when he was playing so deep and so far away from the Watford goal and, after making little impact in the first five games, Mourinho has two options when it comes to utilising the Frenchman.
He must either drop the 23-year-old (which seems unthinkable given the price tag) or consider changing his system to better accommodate his record signing.
Mourinho did try this on Thursday in the Europa League when Ander Herrera started alongside Fellaini with Pogba pushed further up, but he was as equally as ineffective.
The Pogba question is just one of a number of early stumbling blocks for Jose at Old Trafford.
The positive however, came not from Pogba, but a player who continues to surprise and delight with his fearless and direct style of play.
Most of Mourinho's side toiled and were turgid, but the rise of Marcus Rashford continued as the 18 year old England striker scored again for his 10th goal in 23 appearances.
He started and finished the move that led to his goal and looked bright, lively and energetic throughout - the only bright spot on another disappointing outing for the team.