West Ham manager David Moyes has confirmed that Edimilson Fernandes may need surgery on his ankle problem, with cover likely to be brought in during the January window.
The Swiss midfielder has only made nine appearances in all competitions for the Hammers this season and hasn't played since the 2-1 defeat to Manchester City at the start of December.
Moyes, writing in his Evening Standard column, said:
"We’re okay with forward players but, against Arsenal, we had no midfielders on the bench and Edimilson Fernandes may need surgery on an ankle problem.
"Cover may be a priority in January."
Fernandes moved to West Ham in August 2016, after a £5.7m deal was agreed with former club FC Sion.
West Ham already tried to improve their midfield last summer with a move for Sporting's William Carvalho, but the £22m move failed to materialise.
West Ham currently sit 15th in the Premier League table, following a less than impressive start to the season, which saw former manager Slaven Bilic sacked in early November.
Moyes didn't mention any specific targets, but said he would work with the club in regards to anyone the club officials had in mind.