The 2010 Man of Steel, who has played in just two of the Warriors' last five matches, sustained a knee injury in Sunday's Super League match against Hull which he discovered will sideline him for up to six weeks. Richards scored a hat-trick of tries and kicked seven goals in a 56-12 win at the KC Stadium before limping off.
"It is a shame to lose Pat," said Wigan coach Shaun Wane. "I thought he was terrific at Hull. He has had a scan (and) will go and see the surgeon. He could be out for anything between four and six weeks."
Wigan suffered no other injuries from the visit to the KC Stadium while prop Lee Mossop is set to return against Featherstone.