The scrutiny is relentless, and losing 4-1 to Manchester City allowed free reign to condemnation and doubt.
Under Sir Alex Ferguson, United bought into the assertion that individual triumphs and setbacks should not alter the approach to developing a team and an ethos. Moyes' spirit and resilience were as much a factor in Ferguson's decision to anoint him as his successor as his fellow Scot's natural authority and contemporary approach to tactics and sports science. Now, when reputations are being assailed, it is that strength of character that Moyes will rely upon.
Wayne Rooney has already identified tonight's visit of Liverpool in the Capital One cup as the perfect opportunity for United to work through their anger. The competition has been belittled by the glamour and intrigue of the Champions League, but Moyes cannot afford to treat it as an afterthought. There was a sense of anxiety to United's work in the transfer market last summer, even if at the time the club was intent on seeming composed. The pursuit of Cesc Fabregas told of the need to restore the club's image of being unassailable to their rivals, while the suggestion by the Real Madrid president Florentino Perez that United attempted a late bid to gazump his club's signing of Gareth Bale is an indication of the acceptance at United that the team lacks a player of irrepressible brilliance.
United needed a signing that rebooted the purpose and ambition of the squad. Individuals will still maintain their standards, and it was a blow for United that Robin van Persie missed the game at the Etihad due to injury. Rooney continued his personal renaissance but United's fallibilities were laid bare. Liverpool have already exposed them, winning 1-0 at Anfield in the league earlier this month, and only once in the past 10 years have United lost twice in the same season to their great rivals. Moyes will keep encountering measures of Ferguson's dominance, but then the most significant was always his haul of trophies.
During his 27 years at Old Trafford alone, he won 38 competitions, and seldom suffered barren seasons. There were times when he had to make do with the League Cup, and Moyes might also come to value the tournament's worth to his own reign. It is too early to dismiss the worth of any of the challengers for the Barclay's Premier League title - City have looked mundane themselves on occasion, while Chelsea have problems to solve, Arsenal cannot call upon strength in depth and Tottenham Hotspur are still building their belief as much as their merit - but Moyes needs to prioritise establishing himself over more conventional squad rotation issues.
Liverpool will be strengthened, by the return of Luis Suarez but also by not having European football obligations of their own. United, in turn, must seek to rediscover that indomitable spirit that Ferguson worked so hard to entrench in every aspect of the club's football operation. In the aftermath of the derby defeat, Moyes spoke about expecting a reaction from his players. There are other problems to solve, most notably the balance of his midfield and the successors to Nemanja Vidic and Rio Ferdinand in central defence, but Moyes must first maintain United's standards. Van Persie will miss tonight's game with injury, so there would be an opportunity to play Shinji Kagawa in the No.10 role behind Rooney at centre-forward, but the former Borussia Dortmund attacker has been peripheral under Moyes.
There are few options to revitalise the team, since even on route to winning the title last season United's squad was considered ordinary in comparison to previously dominant groups. Ryan Giggs could offer experience, Tom Cleverly could continue his development, Nani could try to reclaim his eminence, or Adnan Januzaj, the 18-year-old Belgian winger, could impress again with his pace and skill. Otherwise, though, Moyes must revitalise through his own authority. The players are said to be impressed with his attention to detail, the greater intensity to the training sessions, and his presence, since Ferguson was seldom seen on the training ground.
There is no depicting United as a club in crisis, or Moyes as a manager in peril. The Old Trafford board provided him with a six-year contract, which was an implicit acknowledgement that the squad needs to be rebuilt. That has to be achieved without lessening the old values of competitiveness, gritty resolve and arrogance. Liverpool would relish causing further disquiet, but that in itself provides Moyes with a further cause. A domestic cup tie in September is seldom considered pivotal, but this is an encounter United will need to approach in an adamant frame of mind.
"I don't think it was ever going to be the case this was going to be easy and smooth after Sir Alex," Moyes said. "Any game after you've had a defeat, you want to get back. [Liverpool] is an important game for us - we want to do well in all the cup competitions.
"It's a big rivalry. And it could take on a bigger significance than people might expect. The cup has been a route to giving young players an opportunity. [But] obviously this is a really big tie."
Statistically, this has been United's worst start to a league season since 2004. That kind of distinction can be undermined by a run of victories, and it is too early to reach for any judgements. Moyes speaks to Ferguson after every match, a routine they have both become comfortable with, and the succession will take time to complete. Ferguson found adversity, too, but he never allowed it to waylay him. That is one attribute Moyes will need to share with his predecessor.