West Brom captain Chris Brunt has been ruled out for five to six weeks due to a knee injury, the club have announced.
Brunt had to come off in the 65th minute of Saturday's 3-0 Barclays Premier League loss to Manchester United at The Hawthorns.
And Albion announced on Wednesday morning that the 29-year-old Northern Ireland midfielder had sustained medial ligament damage.
The Baggies - currently 17th in the table, clear of the relegation zone on goal difference alone - also had midfielder Claudio Yacob (hamstring) and defender Steven Reid (knee) depart the field at the weekend due to injuries.
Both players are doubts for Saturday's clash with Swansea at the Liberty Stadium, while defender Diego Lugano will definitely miss out.
Lugano is another to have suffered medial ligament damage, sustaining the injury last week while on international duty with Uruguay, and West Brom said on Wednesday he will be sidelined for three to four weeks.
The club have also reported that full-back Billy Jones, who missed the United match due to a hamstring tear, is making "good progress in his recovery".
Striker Nicolas Anelka will sit out the Swansea fixture as his five-game ban over his 'quenelle' celebration continues.