United look to continue their push for the Champions League spots, having got back on track last Sunday with the 3-0 win over Leicester City.
They will look to continue their winning run on Saturday when Walter Mazzarri's side come to visit, and they will face a tough test against the Hornets.
They were heavily beaten 3-1 at Vicarage Road back in September, and Mourinho shared his concerns about taking on Watford once again.
“I know they are very difficult," Mourinho told manutd.com. "They are very defensive but there are teams that are defensive and not well organised."
"That's not Watford's case," he stressed. "Walter [Mazzarri] is a very good coach."
"The team is very well organised," he added. "Then they have this capacity of being dangerous on the counter-attack and at set-pieces with a very physical team.”
Convinced he will stay
One player that has been crucial in United's return to form has been Zlatan Ibrahimovic, who has an substantial impact on the side since his arrival last summer.
The Swede scored his 20th goal of the season on Sunday, and Mourinho stated he expects the final year on his United contract will be his last at the top level.
"I'm totally convinced he is going to stay," he said. "He came with the intention to stay two years."
"But in the minds of everyone the first year is going better than every expectation," the coach stated. "He knows we are going to try again to improve next season."
"Try to share with him in a fantastic way," the 54-year-old affirmed. "Probably the last year of his career at the highest level."
"So I'm convinced that he's staying," Mourinho concluded. "He's adapted to the club, to the situation."
Manchester United will take on Watford at Old Trafford on Saturday, February 11 with kick-off at 3pm GMT.