Jose Mourinho says there are "many different reasons" why Manchester United are struggling this season and admits it would be unacceptable to go five matches without a win.
The United boss held a three-minute press conference on Friday morning where he only answered questions about Saturday's game against Newcastle.
When asked why United are struggling this season, Mourinho replied: "For many different reasons."
The Portuguese refused to tell reporters any of those reasons and did not respond when asked if he could assure United fans that he was doing everything he can to try to turn things around.
Sky Sports News reporter James Cooper says Manchester United manager Jose Mourinho looked the lowest he had ever seen him.
United have gone five games without a win just once since 1999, and when it was put to Mourinho that such a sequence for a club of United's size is not acceptable, he said: "Yes, I accept [it is not good enough]."
United sit 10th in the Premier League and although Mourinho isn't reading much into the league table so early in the season, he admits United need a positive result against Newcastle Saturday after taking one point from their last two games.
"At the beginning of October, you look at tables around Europe and in many of the leagues, the tables don't reflect what is going to happen in a few months or even at the end of the season," he said.
United have not won at Old Trafford since the 2-1 victory over Leicester on the opening day of the season, and Tuesday's goalless draw with Valencia extended their winless run at home to four games.
"Only one defeat at home all season [to Tottenham on August 27]," said Mourinho. "Only one defeat in the last seven matches. But no victories at home in the past three matches - three draws.
"Not the feeling of the defeat but not the happiness of the victory. It's important to us to try and win this match."
Newcastle have to yet to win this season, losing six of their eight games in all competitions, but Mourinho says it would be folly to underestimate a side coached by Rafa Benitez.
"A very good coach and a team that is always very well organised, especially against the teams in the first part of the table," said Mourinho of Newcastle and Benitez.
"Their manager is very bright on his analysis of the opponents' qualities and trying to stop them.
"The results they had against the top teams didn't get them points yet this season but gave them very close results and difficult matches for the opposition. We expect a difficult match."