Molloy has made 40 appearances for the Wildcats since joining from Huddersfield in April 2013.
Meanwhile, centre Bill Tupou will also miss Saturday's Challenge Cup semi-final at Warrington after suffering a minor tear in his hamstring.
"The injuries are a loss but we've got depth in the squad," head coach Chris Chester told BBC Radio Leeds.

The Cardiff teenager, fresh from his A-levels, bowled top-scorer Ben Duckett for 80 with the ball before lunch, and later ran through the lower order, finishing with 5-28.
Earlier Duckett and Rob Newton (78) had put on 140 for the first wicket.
Glamorgan reached 23-0 in 11 overs by the close of play.
Northants had looked set for a substantial total as Duckett and Newton sailed along at more than four runs an over against some bowling of variable quality.
But no-one after the openers made a real contribution as the home side lost their last nine wickets for 84 runs.
Carlson, who was picked mainly for his batting, bowled his first three victims and had two caught at cover, while another young spinner, Owen Morgan, took two wickets.
Carlson studied at Whitchurch High School, known for producing Welsh sports stars Gareth Bale, Sam Warburton and Geraint Thomas, and has a place at Cardiff University in 2017 after gaining three A grades in his A levels.
Glamorgan's Kiran Carlson told BBC Wales Sport:
"I was playing in a second-team game at Newport and was told Mesch (Craig Meschede) had failed a fitness test so I had to get to Northampton, it was amazing.
"I'm a batsman by trade and bowl a bit of part-time spin but today it came off, I wasn't expecting to bowl but that one over before lunch saw a bit of spin.
"From there I knew I was going to have to play my part in the game- to make my debut as a batter and get a five-wicket haul was a bit mad, but I'm really happy.
"(At Whitchurch School) they promote sport so much and if you're elite in your sport they just love it and let you get on with training."
Northants opener Ben Duckett told BBC Radio Northampton:
"From the position we were in, it's a pretty poor total after a good start with 140 for one, to collapse like that.
"I thought it was a flat wicket, there was only the odd one in the morning that turned from the left-arm spinner (Morgan), then the right-arm offie (Carlson) on debut ended up getting a five-for but there were a few poor shots including myself.
"We can definitely keep them below 269 if we bowl well with the spinners, the first-innings lead could be very important for us because if the wicket's doing that on day one, I don't know what it'll be like on day three."
Wakefield Wildcats second-row forward Jon Molloy will be out for four weeks after suffering a torn pectoral muscle.
[NEXT_CONCEPT]
18-year-old Kiran Carlson enjoyed a dream Championship debut for Glamorgan, claiming five wickets with his spin as Northants stumbled to 269 all out.