The Sharks went into the match gutted by the ASADA investigation into the club and an injury curse, with seven first graders suspended and another nine in the injury ward.
Add to that the sacked Todd Carney and retired Beau Ryan and there wasn't much left for the club to even field a team.
And it looked as if the Cowboys would cash in, boom lock Jason Taumalolo scoring beside the sticks inside the first 90 seconds of the match.
But while the bookmakers had abandoned them, the Sharks came in full of belief and had the Cowboys stunned as they ran out to a 12-6 lead through tries to Pat Politoni and Feki.
Thurston's class kept the Cowboys in the hunt, the captain earning his side two repeat sets before crossing himself to lock up the scores at the 30 minute mark.
Taumalolo snatched the lead back for the Cowboys in the 58th minute, wrestling his way through a sea of blue for another try sent upstairs to be adjudicated.
Thurston had seemingly iced the game with five minutes to play with his field goal, but Feki scored his double to keep Cronulla in the contest.
Holdsworth then silenced the 11,712-strong crowd when his second attempt at a field goal was successful.
While the win was ugly, it keeps North Queensland's hopes of sneaking into the top four - and the double chance that comes with it - alive heading into round 26.
With a strong for and against record (+176 points) a spot in the top eight is a lock, the Cowboys now needing to beat Manly in the final round and hope Penrith lose to the Warriors to lock up fourth spot.
Cowboys coach Paul Green was relieved with the win and revealed a flu outbreak in his squad had hindered the side.
"We were considering not training at all because we had so many blokes who had the flu," he said.
"Not making any excuses, I didn't think it was a particularly bad performance ... in saying that I think we've got to pay some respect to the way Cronulla played.
"But some of the guys out there for us were really struggling."
Sharks coach James Shepherd was pleased with how his side toiled.
"It was a massive effort from our boys," he said.
"Inexperienced team, a little bit under strength and obviously some changes in personnel this week due to injury and suspension.
"But they just keep working for each other ... magnificent effort."
- AAP