Despite surviving the October international break and believing he was aligned with United's hierarchy on the team's future direction, Ten Hag was shocked and blindsided by his sudden sacking as manager on Monday morning.
But the Dutchman was effectively a sitting duck since the INEOS-led strategic review in the summer, when his job was actively marketed around Europe before Sir Jim Ratcliffe and Sir Dave Brailsford decided to stick with him - against convention.
The belief that they did not have full conviction in Ten Hag could not be shaken, despite the best efforts to form a strong working relationship between the manager and the new leadership group during pre-season.
CEO Omar Berrada, sporting director Dan Ashworth and technical director Jason Wilcox were supporting arms during the tour of the United States, so much so that sources had declared Ten Hag's position as the most solid it has been since the day he won the Carabao Cup.
TrendingEven then, through the positivity in Los Angeles, there was the admission that at the earliest sign of trouble, the speculation around his job security would become unbearable.
And so after just four wins in 14 games across all competitions this season and 115 days since United activated the option his contract by 12 months, Ten Hag is gone.
He had to deal with a ridiculous scale of off-pitch turbulence and still delivered two trophies, but never instilled an identity and clarity during his time in charge with some major tactical deficiencies - like a poor rest defence - continually repeating.
Ruud van Nistelrooy, added to the coaching staff this summer, has been placed in interim charge in a situation that was foreshadowed far and wide. The club legend's appointment was met with comments that INEOS hired him to step in when Ten Hag had to be shipped out, but it was actually the manager that brought him on board.
Sources close to Van Nistelrooy suggest he will not be viewing the job in a temporary capacity and will give everything to steer United in the right direction. He already commands the dressing room and is held in high esteem by the sporting structure.
It has been noticeable too that leading into the October international break, Van Nistelrooy has been a more authoritative influence on the touchline and in engaging the officials.
United had been working through contingency plans in recent weeks to prime for Ten Hag's sacking and the presence of Van Nistelrooy offers the leadership team the time and space to follow a thorough process in appointing the next manager.
News understands a shortlist of around five managers have been analysed and INEOS would ideally want a progressive and proven winner.
Ruben Amorim has emerged as an early frontrunner with Man Utd in talks with Sporting over appointing the 39-year-old.
United distanced themselves from links to Xavi last week, but that could have been because Ten Hag was still in post.
While the Spaniard has an enormous reputation, experience of dealing with expectation and scrutiny at one of the world's biggest clubs, plus a LaLiga title as manager, the former Barcelona tactician's playing style clashes with the direct, counter-attacking strengths of United's squad.
Sebastian Hoeness, Edin Terzic and Thomas Frank have been mentioned to some degree in recent weeks, with the latter having been spoken to in the summer already.
There is a school of thought that United should mirror their statement off-pitch appointments - like landing Berrada, Ashworth and Wilcox - by doing everything necessary to get a truly elite manager through the door.
The one name that has stuck at United since he moved from Hoffenheim to RB Leipzig is Julian Nagelsmann. However, the feasibility of getting him out of his contract with Germany and the financial cost of doing so might be prohibitive.
United have to be conscious of PSR responsibilities and this could sway their decision-making with out-of-work managers that don't require compensation more attractive.
Ten Hag's sacking is set to cost United in the region of £13.5m.
Thomas Frank
The Brentford boss has impressed throughout his six-year reign in west London and has previously been linked with the role when United reviewed Ten Hag's position at the end of last season.
Speaking to the media in the aftermath of the United job becoming vacant, Frank said: "I am very happy here, it's one of the best clubs in the world. What happens in the future, who knows.
"I will repeat myself. I'm very happy here and can see myself being here for a long time. If something comes up, let's see. Now? No. Very happy.
"If I suit, whether that is Man United or another club, that is not for me to judge."
Ruben Amorim
Amorim is another name to emerge as an option for United to turn to, having already been linked with a move to the Premier League with Liverpool, Tottenham, West Ham and even City with Guardiola's future at the club still uncertain.
"I was already expecting this question and obviously I'm not going to talk about the future, because otherwise I'll always have to comment," he said when asked about the job. "I'm very proud to be Sporting coach, that's all."
Graham Potter
The former Brighton and Chelsea boss has been out of work since leaving Stamford Bridge in 2023 and News previously reported that he was one of the candidates INEOS would consider in the event Ten Hag was sacked.
Ratcliffe and his team are known to have met with Potter previously and considered him for the role at Nice, which is another club owned by the company.
Potter appeared on Monday Night Football earlier in the season to comment on his next move in football, where he said: "I'm open to anything, to be honest.
"I've had a fantastic journey over the last 12 years from the fourth tier of Swedish football to the last eight of the Champions League and I would like to spend the next 12 years in the same position, developing players, teams, working with people and making a difference.
"Wherever that is, I'm open to everything."
Gareth Southgate
The former England boss is highly regarded at United given his close relationship with Brailsford and after working with Ashworth in the FA - but has played down his chances of returning to management in September.
"I won't coach in the next year, for sure," he said. "I'm certain of that. I need to give myself time to make good decisions. When you come out of a really big role you need to give your body time, you need to give your mind time."
Xavi Hernandez
Despite the club distancing themselves from the links, Xavi has been open about his ambitions to work in England one day.
Speaking to The Times in 2021, he said: "So why not? I could see myself [managing] in England, definitely. It's one of the things I'd like to experience in my career."
Other potential options
As previously noted, a list of around five candidates has been drawn up for the role but this will not prevent other names circulating as potential successors.
Ipswich boss Kieran McKenna's representatives previously met with United given his impressive tenure at Portman Road and the back-to-back promotions he secured to guide the Tractor Boys to the top-flight.
While former Real Madrid manager Zinedine Zidane is another name that has refused to rule out a move to the Premier League one day, although his decision would likely hinge on United's chances of winning a trophy.
Speaking to French outlet L'Equipe back in 2022, he said: "Never say never. Especially when you are a coach today. If I go back to a club, it is to win. I say this with all modesty."