United came from 2-0 down to force a penalty shoot-out on Wednesday, but then lost 12-11 in a penalty shoot-out as summer transfer window signing Bryan Mbeumo hit the crossbar with what proved to be the decisive kick.

A crestfallen Amorim, who had not watched the shoot-out but preferred to sit in the dugout, said afterwards: "I felt my players spoke really loud today what they want."

United ended last season a lowly 15th in the Premier League table, their worst finish since being relegated from England's top-flight in 1974.

But there had been hopes a full pre-season for Amorim allied to some £200 million ($269 million) worth of new talent up front would lead to a revival in United's fortunes.

United, however, have started this season with a home loss to Arsenal, a draw away to Fulham and a woeful defeat by fourth-tier Grimsby that has led to speculation about Portuguese boss Amorim's position at Old Trafford just three games into the campaign.

Speaking on the BBC's The Wayne Rooney Show, United's record goal-scorer said: "Just the way they lost, it was disheartening. There's something not right.

"I think that's clear. I think the manager said that after the game and I think that's clear for everyone to see that there's something not right there.

"So the issue now is we're seeing very similar performances, similar results and even though it's only three games into the season, it's getting to a point now where you're like... what is going on?"

The former England striker added: "The biggest concern is the manager saying that, his words after the game were damning on the players and obviously being in a position where I've been in that dressing room, if your manager comes out with those words, there's something broken."

Rooney suggested Amorim, who took charge in November after United sacked Erik ten Hag, could be struggling with the demands of managing one of the world's most famous football clubs after arriving from Sporting Lisbon.

"I think what we forget, he's 40," Rooney said. "He's a young manager. And Manchester United is so different to where he's been before. And you come in, there's the media team, the commercial team, the fans, the media. It's completely different.

"And there's a pressure with Manchester United which he will never have felt before. And when you're not winning games, that can start to get to you and it looks like it was a breaking point for him."