The Red Devils' top-four hopes are looking bleak following defeats to Arsenal and Wolverhampton Wanderers, either side of victory over Watford, and they could do with getting three points on the board this weekend.
As well as seeing their Premier League campaign derail over the past month with those back-to-back away losses, United have also exited the FA Cup to Wolves and trail Barcelona 1-0 following the first leg of their Champions League quarter-final.
That high-profile tie, settled by an unfortunate Luke Shaw own goal, was supposed to take priority for Ole Gunnar Solskjaer this week, but instead the Red Devils need to focus on picking up victory against West Ham if they are to avoid being cut off in the race for a top-four finish.
With six league matches to go, United are down in sixth place, two points adrift of Arsenal and three behind Tottenham Hotspur in the final Champions League berth. Third-placed Chelsea are five points better off, meanwhile, albeit having played a game more.
Missing out on the Champions League next season could potentially be disastrous for United, amid reports that certain big-name players face 25% pay cuts, potentially forcing them - Real Madrid target Paul Pogba in particular - to seek pastures new.
This disappointing run of form has supplied ammunition to those that suggested Solskjaer was never the right man for the job, even if he did instigate an incredible turnaround in the three months after replacing Jose Mourinho in the Old Trafford dugout.
Solskjaer, handed the permanent job by executive vice-chairman Ed Woodward a fortnight ago, has a truly massive week ahead to prove those doubters wrong, starting with Saturday's league visit of West Ham.
Two defeats in three Premier League games is as many as United had suffered in their previous 22 in the competition. Worryingly for the Red Devils, they are winless in their last four Premier League games immediately following a European fixture, losing at Manchester City, Liverpool and Arsenal and drawing at Southampton.
With Man City and Chelsea the next two visitors to Old Trafford, this is close to being a must-win game for United. If the feel-good factor brought to the club by Solskjaer is to return, they need to put on a show for their supporters this Saturday.
Recent form in Premier League: DWWLWL
Recent form (all competitions): WLLWLL
West Ham have blown hot and cold in their first season under Manuel Pellegrini, earning praise one moment and then facing criticism the next.
Three losses in their last four matches means that there have been more negatives than positives of late, with the Hammers losing ground in the race for a seventh-place finish.
Should all go to plan and Man City lift the FA Cup next month, the side that finishes seventh in the Premier League will compete in the Europa League qualifiers next season.
That gives Pellegrini's side something to fight for in the remaining weeks of the campaign, yet the Chilean's players appear to have lost motivation since earning a convincing 2-0 win over Newcastle United in early March.
They have since tasted a 2-0 loss away to strugglers Cardiff City, just about carved out a 4-3 win over relegated Huddersfield Town thanks to three late goals, and gone down by that same 2-0 scoreline in games against Everton and Chelsea.
West Ham were poor in the first half at Stamford Bridge and, while they did improve slightly after the restart, they did not do enough to warrant a point against an Eden Hazard-inspired Chelsea. The good news, of course, is that they will not come up against a player of the Belgian's quality in United's ranks this weekend.
Three points from 12 leaves the Irons in the bottom half of the division in 11th place, though they are only five points behind seventh-placed Leicester City, whom they welcome to the London Stadium after this trip to Old Trafford.
United head to Manchester on the back of a run of six defeats in seven Premier League away matches, failing to score in each defeat. The Hammers were unbeaten in five away games prior to this ongoing run (W3 D2).
After winning away against Arsenal, Liverpool and Man City at the start of the 2015-16 season, meanwhile, West Ham are winless 19 away league games against big-six opposition, losing all four this season by an aggregate score of 10-1.
Recent form in Premier League: LWLWLL
United's injury list has still not fully cleared up, as central midfielders Nemanja Matic and Ander Herrera remain doubtful, while defenders Matteo Darmian, Antonio Valencia and Eric Bailly are also expected to miss out.
Jesse Lingard, Anthony Martial, Marcus Rashford and Romelu Lukaku are at least all back in contention, while Alexis Sanchez has built up his fitness on the training ground and is ready for a return, so Solskjaer has plenty of options in attack.
Lukaku has scored in his last five home games against West Ham in the Premier League and has six goals in total during that run.
Elsewhere, Javier Hernandez was hauled off at half time against Chelsea as Pellegrini went with a change of approach - which partly worked - and he will be desperate to start against his former club.
Man United possible starting lineup:
De Gea; Dalot, Smalling, Lindelof, Rojo; Fred, McTominay, Pogba; Lingard, Lukaku, Martial
West Ham possible starting lineup:
Fabianski; Fredericks, Diop, Balbuena, Cresswell; Snodgrass, Rice, Obiang, Anderson; Arnautovic, Hernandez
Head To Head
After winning 11 of their 12 top-flight matches against West Ham between May 2008 and September 2014, Man United have only emerged victorious in two of their last eight such meetings, drawing half of those.
The Hammers won 3-1 in the reverse fixture at the London Stadium in September and are now looking to complete the league double over the Red Devils for the first time since 2006-07.
However, only against Fulham (11), Leeds United and Arsenal (both 12) are the hosts on a longer unbeaten run at Old Trafford in the Premier League than they are against West Ham (10 - W8 D2).
We say: Man United 3-1 West Ham
Man United failed to register a single shot on target against a below-par Barcelona, who were there for the taking. Solskjaer's men have dropped their levels over the past month and a response is needed this weekend if they are to prevent their campaign from spiralling out of control. With West Ham also struggling for consistency, we are backing the home side to come out on top.