Vaz Te dislocated his shoulder during the 3-1 defeat by Arsenal 10 days ago.
"There would have been a slightly quicker option to get him back but we would have been unsure on the stability of the shoulder and it could have been more susceptible to dislocate again," manager Sam Allardyce said on the club's website.
Vaz Te scored a late winner for West Ham against Blackpool in last season's promotion play-off final, returning the club to the top flight after a season in the second tier.
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