The champions have lost their last two top-flight fixtures at Old Trafford 1-0 against Everton and Newcastle. They did win their last league match, coasting to a 3-0 success at Aston Villa last week, but are 10 points behind leader Arsenal.
The Villa triumph was sandwiched by Champions League and Capital One Cup successes against Shakhtar Donetsk and Stoke City, easing 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 Moyes said Wednesday.
Winger Ashley Young scored his first United goal since May 2012 at the Britannia Stadium 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 score sheet; it's been a little while," Young told MUTV. "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 United, which is hopeful of welcoming back Nemanja Vidic, although an immediate return to the first team is not guaranteed for the center back. Marouane Fellaini (back) could also return, but fellow midfielder Michael Carrick (calf) will miss out.
West Ham enters the game in good spirits after an excellent come-from-behind 2-1 Capital One Cup quarterfinal 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 semifinal clash against Manchester City.
West Ham is struggling in the Premier League though, sitting just one point above the relegation zone in 17th. The London club has won just one of its 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 the club goes in search of a first win at Old Trafford since 2007.
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