Manchester United defender Luke Shaw backs head coach Ruben Amorim's tough stance on fixing the club's previously "toxic" and "unhealthy" culture.

Limited to just 12 appearances last season due to injury, the left-back missed a substantial portion of a disastrous campaign, with United finishing 15th, the club’s lowest ever final league position in a Premier League season.

In response to last season’s setbacks, Amorim has committed to raising standards in the dressing room, while he has ostracised several players, with Marcus Rashford having already left for Barcelona and Alejandro Garnacho also made available for transfer.

Matheus Cunha and Bryan Mbeumo have joined in big-money transfers from Wolves and Brentford respectively, and Shaw feels Amorim is on the right track.

"It's not hard to see from the outside what it's been like," said Shaw.

"A lot of the time I've been here over the last few years it's been extremely negative.

"It can be quite toxic, the environment, it's not healthy at all. We need an environment that's healthy, that's positive, that's got good energy and happiness. When you have all those things, you feel free, and you express yourself more,” the 30-year-old declared.

Discussing United’s Portuguese head coach, Shaw said: "Ruben brings demands. Mentality is a big thing. He talks a lot about it.

"He demands 100% and doesn't want anything less. If someone's doing 85-90%, it's not enough. I think, especially this year, if you're not doing the right things, you won't play.

"He's extremely tough on the group. He leaves no stone unturned and I think there are no stragglers in this group anymore. I think everyone has to put the team first. He's made that very clear."

With United having ended the season with a starting XI with an average age of just under 23, Shaw believes that the responsibility to ensure standards are upheld rests on the senior members of the squad.

"The more experienced ones need to be demanding more, day in, day out," he said.

"The levels in training, keeping to the times of when we're doing this or that, making sure no one's coming late.

"The manager's not bothered. He doesn't care who the player is. That's how it should be. Whatever he wants, as players, we have to be delivering – and we are fully behind that," he added. 

Manchester United get their Premier League campaign underway against Arsenal at Old Trafford on August 17.

The Red Devils face Bournemouth in the Premier League Summer Series on Wednesday, rounding out their tour of the United States against Everton at the weekend.