Having overseen more than PS600million worth of signings since he was appointed as manager in 2022, the Dutchman's poor recruitment was a major contributing factor in his downfall.
Including loans, United brought in 22 players under Ten Hag. And to his credit - and as he might have mentioned once or twice - he delivered two trophies for the club, a League Cup in his first season and an FA Cup last term.
But a third-place Premier League finish at the end of the 2022/23 campaign followed by coming eighth last season - the club's worst league performance in 34 years - hardly represented value for the money Ten Hag spent in the transfer market.
Not all of United's purchases under Ten Hag have been stinkers: Lisandro Martinez has become a fan favourite, Andre Onana has overcome an error-strewn start to establish himself as a quality goalkeeper and Christian Eriksen has exceeded expectations since arriving from Brentford on a free.
But plenty of Ten Hag's signings have flopped. Here are the 10 worst.
10) Jonny EvansAfter he was released by Leicester in the summer of 2023, Evans started training with his old club, seemingly to keep his fitness up while he considered his options. He was then surprisingly given a short-term contract to play for United again, which was swiftly upgraded to a one-year deal. And he was given another 12 months this past summer.
The 36-year-old, whose career appeared to be petering out after leaving the King Power Stadium, made 30 appearances for United last season and has already played seven times this term.
Evans' appearance on this list is not his fault. He's been fine. Pretty good, even. But the fact that he's playing for United at all - and has been relied upon so heavily - speaks volumes about the club's botched efforts at squad building in the last few years.
9) Rasmus HojlundAfter overcoming a 14-game goalless streak to begin his Premier League career, Hojlund recorded a pretty impressive debut season for United last term, all things considered.
The 21-year-old Dane is gifted but evidently raw. His haul of 16 goals in all competitions was a solid output.
Hojlund could well still develop into a top-class striker, but United needed a more ready-made option to lead their line. He'd have been a sound developmental option, studying at the feet of an established goalscorer before assuming a regular starting role in a couple of years.
But instead United have paid PS72million for a player who - if his progression goes absolutely to plan - might someday be PS72million worth of striker. They'd have been better off spending the money of an actual PS72million striker.
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8) Sofyan AmrabatFor someone who once famously ran down Kylian Mbappe at the 2022 World Cup, Amrabat exhibited all the nimbleness of a cross-channel ferry upon signing for United on loan from Fiorentina last season.
The Morocco international had played for Ten Hag at Utrecht earlier in his career - back when at least one of them still had hair. But the defensive midfielder, signed to plug the gaping holes that had become a regular occurrence in United's middle third, made little impact at Old Trafford, with just 10 Premier League starts.
7) Joshua ZirkzeeA dramatic late winner prodded in against Fulham on his Premier League debut gave the impression that, in Zirkzee, United had found their next goalscoring hero.
But anyone familiar with the 23-year-old Dutch striker's career to this point will not have been wholly shocked by his failure to score in 12 appearances since then.
A PS34million summer signing from Bologna, the former Bayern Munich forward is a striker more in the Roberto Firmino mould of facilitator, rather than the kind of poacher his debut goal suggested - as evidenced by a modest return of 13 goals in 53 Serie A games.
Creating chances hasn't been an issue for United of late; taking them has. Zirkzee has thus far looked the opposite of the kind of centre-forward they need.
6) Matthijs de LigtAnother player who shared a working past with Ten Hag thanks to his beginnings with Ajax, De Ligt arrived from Bayern Munich this past summer having played for some of the biggest clubs in Europe and as a title winner in three different countries.
The PS41million United paid for the Dutch defender looked a decent deal initially. But he also came in with the sketchy distinction of having been sold at a loss by both Juventus and Bayern. Already, a string of costly errors and positional faux pas have given light to his past employers' thinking in letting him go.
5) Wout WeghorstYeah, us neither. This one was baffling enough at the time and makes no more sense in retrospect.
United were short of striking options midway through Ten Hag's first season and budgetary restrictions meant they could only shop in the loan market. But why they thought a player who'd previously struggled with Burnley would thrive for the 20-time champions is a head-scratcher.
The towering Dutch striker made 17 Premier League appearances in his temporary Old Trafford stay, scoring zero (0) goals.
4) Tyrell MalaciaFor a back-up left-back at a club with Champions League ambitions, PS13million is probably about the going rate. In that sense, United's signing of Malacia from Feyenoord in Ten Hag's first transfer window was fair enough.
But the 25-year-old has suffered dreadful luck with injuries since arriving at Old Trafford, making just 22 league appearances over two and a bit seasons. And in fleeting spells of fitness, the 5ft 7ins full-back has looked too lightweight for the Premier League.
3) CasemiroA panic signing made in the hours after United were thrashed 4-0 away at Brentford in Ten Hag's second game in charge, Casemiro initially impressed following his shock PS60million arrival from Real Madrid.
But the 15-time champions of Europe are rarely bested in the transfer market. Their willingness to cash in on the five-time Champions League winner should have sounded alarm bells.
The 32-year-old Brazilian seemed to age in dog years last season, putting in weekly calamitous performances. United would surely have sold Casemiro in the summer, but the PS400,000 a week he earns at Old Trafford proved too rich even for the lavish spending of the Saudi Pro League.
2) Mason MountEven excusing the fact that he has been injured for the vast majority of his United career so far, limited to just seven Premier League starts since signing from Chelsea in the summer of 2023, Mount was a curious use of PS60million.
Mount is a very good footballer with a high pedigree, a Champions League winner with 35 England caps. But it's difficult to envisage any coherent system that includes both he and Bruno Fernandes. It's a tactical riddle that, when Mount was available, Ten Hag never solved.
1) AntonyI don't think we need to explain this one.