West Ham striker Ricardo Vaz Te faces three months on the sidelines after undergoing shoulder surgery.
Manager Sam Allardyce said the 26-year-old Portuguese striker dislocated his shoulder in the Hammers' 3-1 defeat by Arsenal on 6 October.
"We think we've chosen the best option to strengthen the shoulder and get him back as quickly as we can," he said.
Vaz Te, who has one goal this season, fell heavily after colliding with Arsenal goalkeeper Vito Mannone.
West Ham signed the striker from Barnsley for an undisclosed fee in January 2012.
Vaz Te scored 12 goals in 18 matches as West Ham were promoted to the Premier League from the Championship via the play-offs last season, including the winner in the 2-1 Wembley win over Blackpool.
Allardyce said the player, who often operates as a winger, could have returned sooner but keyhole surgery was considered the best option to avoid complications.
"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," he said.
Vaz Te's absence will give several attacking players - including Mali international Modibo Maiga, loan signing Yossi Benayoun, Matt Taylor and Gary O'Neil - the chance to establish a regular first-team place.