When Kobbie Mainoo limped out of Manchester United’s pre-season friendly against Real Madrid in Las Vegas a year ago and began a four-month lay-off, there were no guarantees he would break into the first-team last season let alone end it playing in the finals of the FA Cup and Euro 2024 as a regular for club and country.

Now Mainoo is the example for United’s aspiring young stars to follow, just like Alejandro Garnacho before him. While the United squad have been in Los Angeles for the last two weeks, Mainoo has been enjoying a holiday in the Californian city – although he did drop in on the last day of training at the UCLA campus to wish his teammates well before they flew to South Carolina for the final tour game against Liverpool.

The three-match trip has been an opportunity for the youngsters to shine in the absence of a number of internationals like Mainoo who are taking a break after the Euros and Copa America.

Mail Sport takes a look at some of the top talent coming through and assesses their chances of featuring in Erik ten Hag’s side this season.

HARRY AMASS 4/5

Left-back was the problem position for Ten Hag last season in the prolonged absences of Luke Shaw and Tyrell Malacia, but United may well have a long-term solution in the hugely exciting Amass.

The 17-year-old joined the academy last year from Watford – where he was included in the first-team squad at the age of 15 – after United fended off interest from Chelsea. He signed his first professional contract in March and was an unused substitute against Liverpool a month later.

Amass started the first two games on tour against Arsenal in LA and Real Betis in San Diego ahead of Saturday’s final friendly with Liverpool in South Carolina, having come on for Sam Murray as a half-time substitute in the opening pre-season games against Rosenborg and Rangers. After a shaky performance in Trondheim, the London-born teenager showed why he is being tipped as a star of the future.

‘It’s probably happened quicker than I expected, but that’s the game – anything can happen at any time, said Amass. ‘Injuries come about and you’ve just got to take your chance.

‘No conversations have been had (with the manager) yet, but this pre-season is a chance to prove that if I’m picked I can do it. Obviously we’ll see what happens when Luke and Tyrell come back. My intention is to play first-team football at this club.

‘I think if the opportunity comes, I’ve got to take it with both hands. It could change my career. I’m just waiting for that moment. I’m ready.’

Strong in the tackle and exciting going forward, Amass has drawn comparisons with Shaw. ‘It’s a good comparison,’ says Amass. ‘In my opinion, he’s one of the best left-backs in the Premier League, if not the best for a long time. So I’m not going to complain about the comparison.’

The highlight of his tour so far came against Real Betis in midweek when Amass got down the left flank to whip in a cross for Amad Diallo’s goal in a 3-2 win, and then launched into a full-blooded double tackle on Rodri and Hector Bellerin.

‘You’ve just got to show your aggressive side,’ adds Amass, who was a member of United’s Treble-winning Under-18 team side last season and got a call-up to the England squad for the UEFA European Under-17 Championship.

‘You might be young or smaller than the opponent, but you have to show you are aggressive and don’t back down. Then you can have a good game.

‘I’m comfortable on the ball. I like to dribble a lot, I like to take on players, I like to excite the fans and play exciting football. Playing with Marcus Rashford makes it 10 times easier, he is an unbelievable player. He gets it. He understands my game straight away.’

Shaw doesn’t return to training until next week and Malacia is still at least two months away from playing after missing the whole of last season following double knee surgery. However, United are close to signing right-back Noussair Mazraoui from Bayern Munich, who is also comfortable playing on the left if needed, so Amass may have to wait a little longer for a competitive debut.

Asked about his progress in LA, Ten Hag cautioned that he is still some way behind Mainoo at the stage last summer but has the potential to make the grade.

‘We had it during last season with Kobbie, but he is not that far now at this moment,’ said the United manager. ‘But if we train him well, if we coach him well, then in three months it's possible that he can be on that point.

‘In this moment he needs to catch up and he has to develop some skills to play for Manchester United, competing for the highest positions in the league. But with big talent it can go up very quickly, and that is very interesting to see if he is capable of doing this.’

TOBY COLLYER 4/5

When Ten Hag won the Carabao Cup in his first season, he made a point of sharing the moment with Mainoo on the pitch at Wembley even though the midfielder wasn’t even in the squad. A year later, he was a first-team regular at United.

So when Ten Hag took time out to speak to Collyer after Garnacho and Mainoo scored to give United victory in the FA Cup final against Manchester City in May, it felt equally symbolic.

‘He just said, “take it all in, enjoy yourself and keep working hard – you never know what can happen”,’ Collyer recalls. ‘He’s a really good guy, the manager. With everyone, he tells you what he wants from each player, he tries his best to help you out. At the end of the day, they do everything for us and we have to put it out on the pitch and give everything for them.’

The 20-year-old midfielder stood out in United’s first pre-season friendly against Rosenborg and was rewarded with a start in the second game against Rangers and opening tour match against Arsenal in LA. Collyer was replaced at half-time by Christian Eriksen and then came on as a substitute for the Dane against Real Betis.

Ten Hag, who personally attended when Collyer signed his first professional contract this summer, said after the Rangers win: ‘I always want to make pathways for young players, but they have to earn it. Collyer has now earned an opportunity and we will see how we can progress.’

Collyer joined United in 2022 from Brighton’s academy where he earned a reputation as a powerful, energetic midfielder who regularly ran 13km-a-game. He was called up to first-team training in February and was named on the bench in games before the end of the season.

‘When you're on the bench, I think it's really valuable just to be in and around it,’ says Collyer. ‘Experience what it's like on a matchday, in the changing room, on the bench with a crowd and getting used to it. Now I've managed to get quite a lot of minutes in pre-season, so I'm happy.

‘I'd say a lot of my work is off the ball. Predominantly, I'm a really busy player. I like to get about the pitch and an area of my game I'd like to improve on is in possession so I think the only way you're going to get better is by demanding the ball, getting on it and not backing away from situations.’

Much could depend on whether Scott McTominay, Casemiro and Eriksen stay at United beyond the end of the transfer window, but it would be a surprise if we didn’t see Collyer finally making it off the bench.

ETHAN WHEATLEY 4/5

A son of Stockport like Mainoo, Wheatley succeeded his old teammate as United’s Young Player of the Year last season and also received the accolade of becoming the 250th academy graduate to make his first-team debut.

‘Quite a few of us wanted it and we had a bit of banter about it,’ admits Wheatley who came on as a late substitute against Sheffield United in April, 24 hours after scoring twice as United beat Manchester City in the Under-18 Premier League Cup final, and a week after he was in the senior squad to face Coventry in the FA Cup semi-final at Wembley.

‘The club, its history is of bringing through loads of academy players. The likes of Kobbie, playing with us less than a year ago and breaking into the first-team inspires us and motivates us because we know the pathway is there. If we impress and get the chances that will be given at this club, we'll take them.’

A power and prolific striker of Malaysian descent, Wheatley scored 22 goals in all competitions for United’s youth teams last season.

The 20-year-old played the first 45 minutes against Rosenborg in Trondheim and caught the eye, then started again in the win over Rangers at Murrayfield where he was only denied a first senior goal by defender Dujon Sterling’s last-ditch block. On tour, he has come off the bench twice to play the second half against Arsenal and the final half hour against Real Betis.

With Rasmus Hojlund ruled out for six weeks with a hamstring injury and new £36.5m striker Joshua Zirkzee only a week into pre-season training, Wheatley could be among the substitutes in the opening weeks of the season and is hoping to reap the rewards of working with United’s new assistant manager Ruud van Nistelrooy.

‘Ruud was probably one of the best strikers we've had at the club. As soon as he came in, I've been trying to take tips off him to help develop my game,’ says Wheatley, who has played for England at Under-17 level.

‘I'm just taking everything as it comes, to be honest. Obviously, I had a little taste of it last season. This season, I just want to keep my head down, keep developing as a player and keep impressing. Hopefully I get more chances.’