MANCHESTER, England -- Several teams have got the better of Manchester United already this season, and it's easy to see why. Tottenham Hotspur are revitalised under Ange Postecoglou, Arsenal are genuine title challengers, Roberto De Zerbi's Brighton & Hove Albion are one of the most well-coached teams in the Premier League and Bayern Munich are Champions League contenders. However, Saturday's defeat -- 1-0 at home to Crystal Palace -- is almost inexplicable.

Of all the setbacks Erik ten Hag's team have suffered this season, this is the biggest red flag of the lot. And they are now running out of excuses.

- Stream on ESPN+: LaLiga, Bundesliga & more (U.S.)

Palace arrived at Old Trafford having won just three of their previous 14 Premier League away games and yet still found a way to inflict a fifth defeat of the campaign on United and a fourth in the league. The loss marks United's worst start to a league season for 34 years, and any hope of building on Ten Hag's positive first year as a manager already appears to be in tatters.

With time running out, substitute Harry Maguire pinged an aimless pass off the legs of Alejandro Garnacho and out for a Palace throw-in -- a neat bow on a United performance lacking any structure or cohesion. As the final whistle sounded on the visitors' 1-0 win and their 76-year-old manager Roy Hodgson jogged onto the pitch in the Manchester rain to congratulate his players, boos sounded around Old Trafford.

"I understand," Ten Hag said when asked about the reaction. "When we played at home or away and we play Crystal Palace, we have to win. With all respect, I know every game in the Premier League is very difficult, you have to play your best, and I understand fans expecting a win and we didn't win, we lost."

This was supposed to be the point at which United's season began to turn around. Back-to-back wins over Burnley and Palace (in the Carabao Cup on Tuesday) was the perfect start to a kind run of fixtures that includes seven at home before Nov. 1, but Old Trafford is no longer the fortress it was last season. Brighton inflicted a first home league defeat in more than a year when they won 3-1, but Palace repeated the trick just two weeks later, and there will be plenty of anxiety among fans who turn up here for the game against Galatasaray on Tuesday and against Brentford in the Premier League four days later.

"We've now lost two games in a row in the Premier League [at home] and we have to do better, that is definitely the case," Ten Hag said. "We have to show it in our body language that Old Trafford is a fortress and you can't get anything here and the only thing you can go away with is a loss.

"I think I can't blame the players and say they didn't run. They gave everything, but in the final part, in both boxes, we didn't do well."

The worry for Ten Hag is that nothing seems to be going right. United didn't score enough goals last season but seemingly compensated by keeping clean sheets. So far this season, they've managed just three in nine games in all competitions, while the problems at the other end remain the same.

Marcus Rashford, who got 30 goals last season, has managed just one this term -- the same number as 72 million summer signing Rasmus Hojlund. Rashford was substituted with United still desperately searching for an equaliser, having already been outshone by 19-year-old Garnacho, who came off the bench after an hour.

"I think [Rashford] can do better and I am sure it will come," Ten Hag added. "He works hard and that is what he is doing. He will net and it will come, but it is not going to be automatic. The team has to invest a lot around him. Today, the decision-making was not good enough."

Ten Hag is still without key defenders Lisandro Martínez, Luke Shaw and Aaron Wan-Bissaka, and the Dutchman might feel aggrieved that referee Chris Kavanagh didn't spot a handball against Joel Ward in the second half against Palace, but any more than a passing mention would only paper over the cracks that are running through United's season.

We've been here before. In recent history, both previous managers Jose Mourinho and Ole Gunnar Solskjaer suffered disastrous starts, couldn't stop the rot, and paid the price with their jobs. Ten Hag faces a similar problem and has to get a tune out of his players quickly or -- inevitably -- it will be his head on the block.

He can be happy that, after the full-time boos subsided, he was applauded down the tunnel by the fans in the Stretford End who had stayed until the end. Ten Hag still retains the support of the majority of supporters and club bosses who are trying to break a cycle of sacking managers when the going gets tough. But results won't be allowed to dip forever, and the time for excuses is over.