On the surface, it seems quite simple.
Carrick followed Fletcher’s lead in ditching Amorim’s three at the back formation, pushed skipper Bruno Fernandes into a more forward role, recalled Kobbie Mainoo to play alongside Casemiro and stuck with it.
Across his 10 games in charge, Carrick has made just six changes to his starting line-up.
Two of those were enforced – because of the injuries that continue to sideline Patrick Dorgu and Lisandro Martinez. Of the other four, two were bringing Benjamin Sesko in for Amad Diallo for the home win over Crystal Palace on 1 March, then swapping it back two games later after United had been beaten at Newcastle.
The final pair were Noussair Mazraoui coming in at full-back for Diogo Dalot at St James’ Park, then Dalot returning one game later when Mazraoui was ruled out through injury.
Manuel Ugarte, Ayden Heaven and Joshua Zirkzee have all come on in four games or more. The same is also true of Sesko and Mazraoui.
United’s relative lack of games – they are currently in a stretch of 23 days without one – means rotation is a choice rather than a necessity.
Yet Carrick’s impact goes far deeper.
Club sources note the sense of calm that has settled across the club.
The 44-year-old is a relaxed individual – the epitome of someone who does not get carried away by success or overly despondent by failure.
In public, that comes across in his media briefings.
“I’m not going to sit here and get angry with you if that’s what you’re asking,” was Carrick’s response when he was asked before the 2-2 draw at Bournemouth if he ever used anger as a management tool.
The attitude is in stark contrast to Amorim, who admitted to getting emotional at the performances of his team. That led him to make ill-advised news conference comments.
Rather than being on edge, United’s staff at their Carrington training complex feed off Carrick’s attitude and the feeling is they are delivering more.
Meetings between the head coach and Wilcox are fewer now, it is said, because there are not as many day-to-day issues to address.
Sources who know Carrick say his intention has been to strip training back to basics. That has resulted in the shorter sessions critics have argued show the players are not being worked hard enough.
Carrick’s view is if the basics are right and training hits the right levels, the intent provides more value than extended practice.
Sources close to the players say the squad are unified, happy and enjoying their work.
Understandably, coaches Jonathan Woodgate and Jonny Evans have focused their individual sessions on the defenders. Travis Binnion has focused on the forwards, among whom Sesko is a big fan.
Steve Holland’s appointment is viewed as a masterstroke. His previous relationship with Carrick’s brother Graeme through shared time spent working for the Football Association at St George’s Park was particularly helpful, even if the final decision to bring Holland into the fold was the result of a unified plan.
Twenty-three points from 10 games since Carrick’s appointment is the highest in the Premier League over that period.
Rather than those games against Manchester City and Arsenal being an awful start, they proved to be a springboard.
Victory over Mikel Arteta’s side was the one that really resonated with Old Trafford bosses, proving that beating City – something United had done periodically under a number of managers – was not a one-off.
During this period, some of the alternatives to Carrick for the permanent role have either suffered reputational damage or become unavailable – Roberto de Zerbi would become the latest if he accepts the Tottenham job.
United’s stance remains they do not want to be bounced into an appointment, and will take their time reaching a decision.
The reality is they are yet to speak to anyone else.
There are some elements of Carrick’s management that cannot be answered this season – including how he copes with a 60-game campaign, compared to this one with its optimum preparation time, which has allowed Luke Shaw, Harry Maguire and Casemiro to play every game under him.
There is also the reality that after pushing for Amorim’s appointment, Wilcox and chief executive Omar Berrada risk their own reputations if they get another major call wrong.
Nothing is certain until an appointment is made, but if United maintain their momentum and qualify for the Champions League, it is hard to imagine Carrick not being given the job.