Manchester United have four first team squad members on loan and all will return to Old Trafford at the end of this season. They've had largely positive seasons, too, though whether they'll still be with their parent clubs at the start of the 2019-20 campaign is as yet unclear.

Dean Henderson, 22, has enjoyed the most success as a goalkeeper for a Sheffield United side that has won promotion to the Premier League for the first time since 2007. He has kept 20 clean sheets and was voted the club's young player of the year. He's keen to stay for another year in Sheffield and play Premier League football rather than return to Manchester as the third- or even fourth-choice goalkeeper.

Henderson, from Cumbria (100 miles north of Manchester), joined United at 14 from Carlisle. He is confident and single minded. Jose Mourinho wanted him to travel on the club's 2018 preseason tour to the U.S. but Henderson questioned why that would be a good idea, suggesting that it would be better if he did preseason training with a club for which he was likely to play first-team football. Mourinho couldn't argue with that and he moved to Bramall Lane.

-- Keep/Dump: Who has a future at Man United?

-- Man United would be foolish to let Pogba go

-- De Gea becoming a liability

Loan moves at successively bigger clubs in higher leagues have helped the England Under-21 regular. He joined Sheffield United after spells at Stockport County, Grimsby and Shrewsbury Town, where he was named in the team of the year for the division. Manchester United rate him and have watched him in every game he has played on loan. The club thinks he needs to be more consistent and continue his development but with questions over the futures of David de Gea and Sergio Romero, it doesn't harm to have a young talented goalkeeper on your books who has shown he can be a regular in the top flight.

Mourinho praised another 22-year-old goalkeeper on his books, Joel Castro Pereira. The Swiss-born Portuguese national is on loan at Belgian first division side Kortrijk until the end of this season, having spent the first half of it in Mourinho's hometown of Setubal in the Portuguese Primeira Liga. That loan spell was cut short in January. United wanted him to get as many games as possible and signed Lee Grant as the third-choice goalkeeper knowing Pereira, who also played an EFL cup game in 2017, would be away.

Pereira, known as "The Cat" by teammates, has, however, been unable to get as many games as Henderson, an ever-present for Sheffield United and it now has been two years since he made his one Manchester United appearance against Crystal Palace. He has a contract until 2021.

Axel Tuanzebe is another who has enjoyed a fine season in the Championship, playing as a central defender for Aston Villa. The 21-year-old, who was born in DR Congo but moved to Greater Manchester at the age of 4, has captained every United team except the first team. Fast, strong and composed, he can also play at right-back. He's intelligent, driven, motivated and had been one of Aston Villa's best players apart from the three months he was out with a metatarsal fracture, an injury he picked up just before Christmas.

United have also had him watched in every game. The club's academy boss, Nicky Butt, feels he has what it takes to play in United's first team, while Tuanzebe had really enjoyed working with Villa's assistant manager John Terry, from whom he rightly feels that he can learn a lot. Tuanzebe was a childhood Chelsea fan who'd watch Terry all the time on television.

Dean Henderson has been a revelation between the posts for Sheffield United, helping them get promoted to the Premier League. He reportedly wants to stay there another season, too. Richard Sellers/EMPICS/PA Images via Getty Images

"John always gave me little pointers, whether about my playing style or how to be around people or carry yourself," he told me at the start of this season. "He never took more than three touches in training. The ball moved quickly with him."

Tuanzebe is enjoying playing every week for the first time and with Villa in the Championship playoffs -- they play Norwich on May 5 (7:30 a.m., ESPN+) and the playoffs begin May 11 (ESPN+) -- he could help them return to the Premier League.

Back in July, I asked him where he wanted to be in a year's time. "Ideally, playing for United and England all the time," he said. "Realistically, I need to get big games under my belt." Though he has not appeared in the Premier League yet, at Villa he's turning out in front of crowds touching 40,000. He was excellent at Leeds last weekend.

United are inclined to take Tuanzebe on United's preseason tour of Australia, Singapore and China to give him a proper chance at becoming a first-team player. While fans have talked up buying a new central defender, Ole Gunnar Solskjaer has been largely satisfied with his central defenders.

Axel Tuanzebe arguably has the brightest future at Man United but is set to spend another year away next season to get ready. Neville Williams/Aston Villa FC via Getty Images

The prospects are not as bright for another defender, Timothy Fosu-Mensah. Unlike Tuanzebe and Henderson, the 21-year-old hasn't kicked on as hoped. He has all the talent to become a top footballer -- his speed and strength stand out -- but he has not convinced on loan. Unfortunately, he returned to Manchester last week after a year on loan at Fulham to have surgery on a cruciate knee ligament, which he suffered in Fulham's 2-0 win over Everton three weeks ago.

Fosu-Mensah has started just eight games for United since being given his debut by Louis van Gaal in 2016, and been a sub in another 13. In 2017-18, he went to Crystal Palace to play first team football but while he started Palace's first six league games last season -- all of them defeats -- he lost his place in the side when Roy Hodgson took over to the excellent Aaron Wan-Bissaka and wasn't making the matchday squad by the end of last season.

Hodgson is a respected, old-school coach but was reportedly frustrated with Fosu-Mensah's inability to take in and act on information communicated to him by coaches. That said, Leroy Sane described Fosu-Mensah as the toughest defender he'd faced last season when he was at Palace.

The Amsterdam-born defender with three full Holland caps went to Fulham this term but started only 10 games and again, wasn't even making the matchday squad for most of the season. His talent wasn't doubted, unlike his ability to implement his coach's thoughts. He did battle his way into the squad in March and played against Liverpool, Manchester City and Everton before the cruciate injury. Like Tuanzebe, Fosu-Mensah can play central defender or right-back. While he's out injured he will receive support from Manchester United, where he has a contract until 2020. If he's to make a career at Old Trafford, though, his fortunes would have to improve drastically.

All this is a bonus for Solskjaer who will know all about these young talents but who needs to decide what is right for all of them individually, as well as for Manchester United collectively. Meanwhile, United are already looking to loan some of their talented youngsters out next season.