INJURIES have rocked the Cowboys under-20 side ahead of their clash with South Sydney on Sunday.
Both have managed to train this week but coach Grant Bell conceded they were almost certainly out of the clash with replacements to be named at training today.
In further bad news, forward Leo Faagutu re-injured the ankle he hurt in round one when he returned to the TDRL last weekend.
Captain Ryan Carr said the loss of Thompson especially would hurt the fledgling team which is trying to develop combinations in its debut season.
"I think combinations across the park are important in any position, halves especially," he said.
"But I think they've been going pretty well, they're getting better as the season goes on, they've been clicking.
"I think they're just learning really well and they've started to play some real good footy in the last few weeks, our halves especially."
Despite being unable to snare a win from their seven games so far this season, Carr said the players remained optimistic about turning their season around.
The Cowboys have played two draws and had victory snatched from them in the final minute against the Dragons.
"We're all just staying together as a team and working hard for that win," Carr said.
"We're just working hard at training and in our games.
"I think we've been trying hard but we've been a bit unlucky in a few of our games and soon enough we should get a bit of luck and things will go our way.
"But definitely we're optimistic and there's no frustration."
South Sydney will be bolstered by the addition of dumped first-grader Eddie Paea who will line up in the Toyota Cup as halfback.
"Eddie's a good player, obviously he's played NRL which is a big ask of him," Carr said.
"He's definitely one to watch but we're concentrating on our game."