Jose Mourinho admits Manchester United's lack of confidence has contributed to their dismal three-match losing streak.

Mourinho's side slumped to an embarrassing 3-1 defeat at Watford on Sunday to cap a miserable week that also included losses against Manchester City and Feyenoord.

After winning the first three games of the Mourinho era, United are stuck in a rut and looked painfully short of inspiration in their first defeat against Watford for 30 years.

It was a tepid display that recalled the worst moments of Louis van Gaal's reign and Mourinho believes his players are suffering from a lack of belief that takes an extra toll whenever an important moment goes against them.

"We started the season very well and had good results. I feel the first moment we had a defeat, a difficult situation, some of the boys are having a bit of difficulty coping with the negativity," Mourinho said.

"You see Ashley Young, his mentality the happiness and confidence he brought to the game is something more players need to have."

It is the first time a Mourinho team has lost three in a row since he was in charge at Porto in 2002.

But Mourinho isn't about to panic because he believes United's woes are only partially self-inflicted and he expects a revival once their luck changes.

"I reflect on three factors from the match, but only one of them I can improve," he said.

"The first factor depends on ourselves, it relates to our individual mistakes and collective mistakes as individual players and as a team. We have to improve something, it is in our hands.

"The second factor is the referee and I can't control their mistakes. The story of the game is the result and not the ridiculous situation of the first goal.

“The third factor is luck, we didn't have it. We were the best team when we lost. Heurelho Gomes made a phenomenal save from a Zlatan Ibrahimovic header."