Ruben Amorim has three positions up for grabs in his best Manchester United line up

Ruben Amorim has some tough decisions to make as he looks to make his mark on Manchester United.

The 39-year-old took charge of his first training session on Monday, albeit with a reduced squad due to international commitments, as he looks to make an immediate impact on the club.

Amorim could be without as many as five senior defenders when his side face Ipswich Town this weekend and the United head coach might have to wait a while before he can unleash what he feels is his strongest line up. Even then, there is plenty of debate over what United's best side is, with three positions fiercely up for grabs if they do indeed switch to a 3-4-3 formation, as is widely anticipated.

Andre Onana is a certainty to start in goal, while the strongest back three is also rather straightforward. There is huge hope for Leny Yoro as the right-sided centre-back, with his modern approach viewed as the perfect complement of Lisandro Martinez in the left-sided role. Matthijs de Ligt is the player best suited to the central role, with Harry Maguire out of contract at the end of the season, though the club do have the option to extend it by an additional year.

The first position up for grabs comes at right wing-back, with Diogo Dalot and Noussair Mazraoui both fighting for a starting role in the team. Dalot has played the most minutes of any United player so far this season, which perhaps explains his drop off in performance level, and why he has made so many sloppy mistakes. Mazraoui on the other hand, has been an astute signing, though he is perhaps not as well suited to a wing-back role as Dalot. On the left wing, whether you like it or not, Luke Shaw has to be the starter there when he is fit. His injury issues have become a huge problem, but when available, he is still one of the very best in the world in that position.

Into midfield, there is an expectation Manuel Ugarte will play an integral role under his former Sporting mentor, though there is still plenty of debate about who should partner him. Kobbie Mainoo is the popular choice, yet at such a young age, the hype must be carefully managed and there is fair criticism to be made about the lack of defensive protection their partnership would bring. Casemiro is arguably the most rounded option to play there, though he is clearly on the decline and might not work as a long-term solution as the season progresses. The same can be said for Christian Eriksen, who although has been in fine form, lacks the physicality and fitness to play there twice a week.

Bruno Fernandes is anticipated to occupy one of the attacking midfield slots, but Amorim has favoured wingers in the roles at Sporting, so it is unclear who will partner him. Amad Diallo is the most in form attacking option at the moment, while Alejandro Garnacho and Marcus Rashford will both feel they should be given a chance to play under the new head coach as well. This is arguably the most fiercely competitive of the positionso, given Mason Mount and Joshua Zirkzee are both also contenders to play there as well.

Up front, Rasmussen Hojlund is still the only natural striker at their disposal. Although his performances haven't been good enough this campaign, he has to be given a fair chance under the coach who has transformed Viktor Gyokeres into one of the most lethal finishers in world football.

United's best XI under Amorim (3-4-3): Onana; Yoro, De Ligt, Martinez; Dalot/Mazroaui, Shaw; Ugarte, Casemiro/Mainoo/Eriksen; Fernandes, Amad/Garnacho/Rashford, Hojlund