The Premier League champions have lost their last two top-flight fixtures at Old Trafford 1-0 against Everton and Newcastle United.
They did win their last league match, coasting to a 3-0 success at Aston Villa last week, but are 10 points behind leaders Arsenal.
The Villa triumph was sandwiched by UEFA Champions League and League Cup successes against Shakhtar Donetsk and Stoke City, wins that have eased the pressure on manager David Moyes.
But improvement in the Premier League is essential for Moyes, starting on Saturday, and the Scot will be sweating over the fitness of striker Wayne Rooney.
The England international missed Wednesday's 2-0 win at Stoke with a groin injury and with fellow striker Robin van Persie (thigh) on the sidelines, Moyes will be counting on the former Everton man.
"He has got a chance (of playing)," a hopeful said Moyes on Wednesday.
Winger Ashley Young scored his first United goal since May 2012 and was named the man-of-the-match after an impressive display.
"As soon as I hit it, I felt like it was going in. You could see from my celebration how much it meant to get on the scoresheet; it's been a little while," Young told MUTV afterwards.
"The boys were magnificent – we showed great spirit and character and hopefully we take that into this weekend's game."
Young could retain his place as a result of that performance for a United side who are hopeful of welcoming back Nemanja Vidic (knock), although an immediate return to the first team is not guaranteed for the centre-back.
Marouane Fellaini (back) could also return, but fellow midfielder Michael Carrick (calf) will miss out.
West Ham enter the game in good spirits after an excellent come-from-behind 2-1 League Cup quarter-final win at Tottenham on Wednesday.
Matt Jarvis and Modibo Maiga scored in the last 10 minutes for Sam Allardyce's side as they set up a semi-final clash against Manchester City.
West Ham are struggling in the Premier League though, sitting just one point above the relegation zone in 17th.
The London club have won just one of their last nine league fixtures and picked up just six points from eight Premier League matches on the road.
James Tomkins (groin) did not play at Tottenham and could miss out again, while strikers Andy Carroll (ankle), Ricardo Vaz Te (shoulder) and Mladen Petric (calf) are still on the sidelines.
Also missing for West Ham are defender Winston Reid (ankle) and winger Stewart Downing (calf), as they go in search of a first win at Old Trafford since 2007.
