Michael Morgan, Reagan Campbell-Gillard, Latrell Mitchell and Dylan Napa suffered injury blows during NRL victories for the Sydney Roosters and the New Zealand Warriors nine days prior to State of Origin II.
North Queensland Cowboys and Queensland full-back Morgan's participation in the second Origin game a week on Sunday is in doubt after he sustained a bicep injury in the 23-16 defeat to the Warriors in Townsville on Friday.
The Maroons - beaten 22-12 in the Origin opener - also have a concern over Napa, who suffered a suspected ankle sprain during the Roosters' resounding 32-6 win over the previously in-form Penrith Panthers.
Penrith prop Campbell-Gillard suffered a suspected broken jaw and there was another blow for New South Wales Blues coach Brad Fittler when Mitchell was carried with a neck injury following a lengthy treatment at Allianz Stadium.
Captain Roger Tuivasa-Sheck inspired the Warriors to a victory which consolidated their place in the top four, scoring a superb solo try and laying on another two as the Warriors crossed three times in the space of nine first-half minutes.
Ken Maumalo and Solomone Kata dotted down either side of a stunning score from the skipper, who burst down the middle with a brilliant side-step and showed a sharp turn of foot to go under the posts.
Kyle Feldt claimed a second-half double and Javid Bowen scored the Cowboys' opening try late in the first half, but they were unable to deny the Warriors another win, Shaun Johnson scoring 11 points from the tee.
The Roosters closed in on the top four by ending Penrith's run of four consecutive victories, Blake Ferguson claiming a brace as they scored five tries to extend their winning streak to four despite having only 15 players to call upon for much of the match.
Isaac Liu, Zane Tetevano and Daniel Tupou also crossed for the rampant Roosters, Dean Whare coming up with Penrith's only four-pointer.