Arsenal's injuries, combined with a rejuvenated Sunderland squad under recently hired manager Sam Allardyce, should be a boost for the Black Cats.
"We will go into the big games as the underdogs and tell the lads to enjoy themselves because nobody expects you to get a result," Allardyce said. "Hopefully we can shock one or two because the lads have enough confidence in their ability to play any team at any time."
West Ham, still missing the injured Dimitri Payet and Enner Valencia, also will be without Diafra Sakho against United at Old Trafford after the Senegal striker was ruled out with a thigh injury for up to two months by coach Slaven Bilic on Thursday.
Sakho was hurt in a 1-1 draw with West Brom last week.
"It will be four to eight weeks, maybe more," Bilic said. "He has a bit of history with his thigh. ... Three injuries to our key players, especially in the offensive side of our game, it's a blow."