Manchester United manager Jose Mourinho blamed "individual and collective mistakes" and was critical of referee Michael Oliver after his side suffered a third successive defeat.
United's 3-1 loss at Watford on Sunday followed defeat against Manchester City in the Premier League and Feyenoord in the Europa League.
With the game goalless, Anthony Martial lost possession leading to Etienne Capoue scoring the opening goal and Mourinho felt a foul should have been given for Miguel Britos' challenge. Although Marcus Rashford eventually equalised, Watford went on to win through a goal from substitute Camilo Zuniga and then a Troy Deeney penalty.
Mourinho told BT Sport: "There's no debate, no controversy. It's an obvious situation, like last week against Manchester City, but it's something I cannot control or be critical with. In the first half, for the first 25 or 30 minutes, we didn't play well. That's something we can control and improve, then the referee and linesman's mistake is not under my control. I can do nothing to improve it.
"The second half was much better, we got the draw [equalising at 1-1] then, after that, we were the team [who looked likelier to win]. [Heurelho] Gomes made a phenomenal save [from a Zlatan Ibrahimovic header]. Luck is not something we can control. What we can control is individual and collective mistakes. The second goal is an individual mistake. We know we have to press the wing backs outside the box. Then, another individual mistake [for the third goal]."
When asked if he was concerned, Mourinho replied: "I'm always concerned when we don't get results we want. That's an obvious situation."
Mourinho continued on his theme of the players' errors in his post-match news conference, and said it is his job to ensure they are cut out in future.
"I feel that some individuals probably feel the pressure and responsibility too much," he said. "But from a collective point of view, I only have good things to say about them. At 1-1 everyone thinks we are going to win the game. We were showing complete control, intensity, creation.
"But their second goal is a mistake that goes against our plan and our training, because our intention was for their wing-backs to be pressed and not let them progress. And what happened was the guy gets the ball 20-25 metres away from our box and instead of being pressed, we give him the space to progress. [Nordin] Amrabat receives the ball and our left-back [Shaw] is 25 metres from him instead of five.
"But even at 25 you have to jump and go and press, but no, we wait. This is a tactical but also a mental attitude. It's something that doesn't become perfect in a couple of weeks. So we have to improve, no doubt, individually and collectively. And that's my job.
"We started the season very well with [winning] the Community Shield and three victories in a row in the Premier League, the best start that a new manager has had at Manchester United I think. But was I thinking that my team was ready, perfect, unbeatable? Not at all.
"I was completely aware that we were not perfect, with lots of players who are not end products and can make their own mistakes."
- BT Sport Football (@btsportfootball) September 18, 2016
Asked if he felt referee Oliver should have penalised Miguel Britos' tackle on Martial in the build-up to Watford's opening goal was a foul, Mourinho said: "When you come with that question it's because you know. You don't ask me about that if you think that nothing happened. The reason you asked the question is my answer.
"The referee's crucial mistakes are not in my control, there is nothing I can do about that. That is not under my control. But against Man City you know what happened in minute 55 [when Mourinho felt United should have had a penalty for a challenge by Manchester City goalkeeper Claudio Bravo on Rooney], today you know that happened for the first goal, against Feyenoord there was the offside goal. So we were punished by these mistakes and I can't do anything about it."
Looking ahead, Mourinho told MUTV: "Tomorrow, we have a training session at 10.30 in the morning and we have to be there and we have to work, but they have to show a certain attitude towards the negative moment.
"We need positive people to give us positivity because obviously, the next time that these guys go on to a football pitch, they're going to feel -- as a normal human being -- the weight of the defeat."
Watford captain Deeney felt that his team deserved credit for how they stifled United, saying: "I am not surprised by how we played. We should take a bit more credit, we pressed well, condensed the space and were tough in the tackle. We need to be against teams like Manchester United who have high quality players and spend a lot of money."