West Brom captain Chris Brunt has been ruled out for five to six weeks with a knee injury.
Brunt suffered the injury in Albion's 3-0 defeat by Manchester United on Saturday at The Hawthorns.
Northern Ireland midfielder Brunt was forced off with the injury just after the hour mark and scans have since revealed medial ligament damage.
The news is a blow for Albion's battle for Premier League survival as Brunt is one of Pepe Mel's key players and leaves the Spanish manager facing a potential injury crisis for the weekend.
Claudio Yacob and Steven Reid were also substituted along with Brunt against United due to injuries.
Midfielder Yacob suffered a tight hamstring and is a doubt for Saturday's trip to Swansea along with Reid, who limped off with a knee injury.
Fellow right-back Billy Jones is making good progress in his recovery from his hamstring tear suffered against Fulham 17 days ago but he faces a race to be fit for the trip to the Liberty Stadium.
The Baggies are already without Diego Lugano for up to a month due to medial ligament damage sustained while on international duty with Uruguay last week.
Striker Nicolas Anelka will sit out the Swansea fixture as his five-game ban
over his 'quenelle' celebration continues.