The Premier League champions sit ninth in the table after 15 games and a massive 13 points off leaders Arsenal after back-to-back defeats at home to Everton and Newcastle in the space of four days.
United face Shakhtar Donetsk in their final Champions League group game on Tuesday, the competition where Moyes has enjoyed some success with their progression to the last-16 already ensured.
But he revealed he is taking full responsibility for their poor start in the Premier League in their first season since Alex Ferguson retired.
“We’ve been inconsistent at times but played well in some of the Champions League, not so well in the Premier League,” he said.
“We’ve maybe lacked a bit of fortune in some of the games.
“It’s tough because the expectancy is to win all the games.
“I think there’s a bit of everything we can improve – generally play better, pass better, defend better.
“It is not any one thing. It is all round we have to improve. It was only recent when we had beaten Arsenal here and then Leverkusen (that) we were speaking very well about the team.
“I take complete responsibility for the results. Fortunately they’ve been good in the Champions League but not in the Premier League. Hopefully they will get better.”
Moyes revealed the shock defeat by Newcastle on Saturday – the Magpies’ first league win at Old Trafford since 1972 – has only given the United manager more drive to turn their season around.
“No I did not need to lift my spirits after Newcastle – that raised my spirits,” he said. “It just made me more determined to make sure we improve and get better.
“I agree in recent games we have not finished games in the way we would have liked to. I’ve tried to make changes but it hasn’t quite happened.”
The United boss revealed the players are hurting but still has full belief that they will turn their season around and that he has a squad big enough for the challenge.
“Yes the players are hurting because they are used to winning and when they don’t that hurts,” he said. “They care very much about their team and their club. They will respond, there is no doubt about that.
“The question I got asked was if the squad big enough and I said, ‘yes the squad was big enough’. I believe the squad is big enough.”
Moyes revealed he may make more changes for their final Champions League group game on Tuesday with qualification already sorted and a Premier League clash with Aston Villa on Sunday to come, but he still has one eye on topping the group in a bid to avoid some of the bigger sides.
“It is important to give yourselves the best possible chance in the next round but the big job was to make sure we qualified,” he said. “That part is done. Hopefully we can finish off the group unbeaten and that will see us through.
“There is a little bit of that (resting players) in our thinking but also there are one or two injuries which we will have to take into consideration.”