Six has been the magic number for Ruben Amorim in his first few weeks as Manchester United head coach.

Tthe United boss made six changes to his starting line-up for the third game running for Wednesday night's 2-0 defeat to Arsenal at the Emirates Stadium. Amid a hectic fixture schedule, the 39-year-old, who was appointed as Erik ten Hag's successor last month, has found it impossible to avoid tinkering with his starting XI.

Twenty different players have started under Amorim in his first four games at the helm. That tally could increase to 21 when Nottingham Forest visit Old Trafford this teatime, after Leny Yoro made his long-awaited debut as a second half substitute against Arsenal in midweek.

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The Frenchman, who joined United from Lille in July, stepped off the bench with 59 minutes played, replacing Harry Maguire. He did well in challenging circumstances, producing three tackles, two clearances and one interception in just over 30 minutes.

Having made his United bow via the bench, Yoro, who suffered a fractured metatarsal in the opening game of United's pre-season tour of the United States in July, will now be dreaming of making his first start for the club and earning his full debut.

In north London Yoro slotted in as the right-sided centre-back - the position which Matthijs de Ligt had occupied from the start. The Netherlands international had moved across to the right after the returning Maguire was deployed in the centre.

De Ligt is one of just four players who have started the four games of the Amorim era, alongside Andre Onana, Noussair Mazraoui and Bruno Fernandes. Should De Ligt maintain his run of starts against the Midlands outfit, all eyes will be on who starts alongside him. Lisandro Martinez is back available after missing out against Arsenal through suspension and he is likely to reclaim the left-sided centre-back berth.

That could leave Yoro, Mazraoui and Maguire squabbling for the last remaining centre-back spot. The general consensus is that Yoro will eventually become United's first-choice in that position but Mazraoui deserves enormous credit for his performances in the role against Ipswich Town, Bodo/Glimt and Everton. The versatile Moroccan started as the left-sided centre-back against Arsenal in Martinez's absence.

Mazraoui, who was originally signed to operate as a right-back, is the most versatile defender in United's ranks, seemingly capable of playing anywhere across the back line. It is not beyond the realms of possibility that we will see him operate as a wing-back at some stage in the coming weeks.

If Yoro gets the green light to start against Forest, it is possible Mazraoui could occupy the left-wing back berth, with Diogo Dalot making way. Amad has to be recalled to the right after being benched against Arsenal.

United have made it crystal clear they will not rush Yoro's comeback, meaning Amorim might refrain from throwing him in from the start after just one substitute appearance. However, he is now locked in a three-way battle to try and complete the first-choice defence.