The 35-year-old England prop forward is due to have surgery this week to repair the damage in his left arm which he sustained in the opening minutes of last Friday's 24-16 victory over Catalan Dragons. He left the field in the seventh minute and took no further part in the game.
"He's having to have an operation on his bicep so he's going to be missing for eight weeks, maybe longer," coach Tony Smith told BBC Radio Merseyside.
Morley's latest injury setback looks set to scupper his hopes of playing in a third World Cup at the end of the season and must cast a doubt over his career.
The former Leeds and Sydney Roosters forward turns 36 in May and is out of contract at the end of the year.
Morley was hampered by a career-threatening neck injury last season and, although he returned in time to lead Warrington to a third Challenge Cup success in four years and a maiden Grand Final appearance, he warned at the start of this season that another injury-hit year could prompt him to hang up his boots.
"I was disappointed with last year and, if it got to that stage again, I'll just call it quits," he said at the club's pre-season media day.
The Salford-born player was recently the subject of interest from the City Reds' new owner Marwan Koukash, which prompted his club coach Smith to insist he remains part of his plans.
Morley, who is the only Englishman to have won Grand Finals on both sides of the world, became the most capped British player in rugby league history when he made his 50th international appearance in the 2011 Four Nations final and earned an England recall for the 2012 autumn international series.