The Cowboys first took the lead four minutes from time in Townsville when Michael Morgan's field goal flew over shortly after Reynolds hit the uprights with his own drop-goal attempt at the other end.

The Rabbitohs marched downfield with less than a minute on the clock but as the No.7 attempted another shot to put the game into golden point, Jake Granville was caught offside leaving Reynolds with an easy kick in front.

Meanwhile, Queensland coach Kevin Walters, after having to get used to life without Cameron Smith, looks likely to have to deal with being without Scott for at least Origin Game 1 with the veteran limping off in the second half.

Earlier, Rabbitohs hooker Damien Cook scored a try and set up another for George Burgess, in a timely boost to his chances of winning an Origin call-up for the Blues.

His try would have been the highlight of most games as he picked up the ball on the fifth tackle and weaved around Frances Molo, Ben Hampton and Corey Jensen at top speed before touching down under the posts.

Of minor solace to the Maroons will be the form of Morgan who produced two superb assists for Antonio Winterstein in each half to score the Cowboys' two tries.

The Rabbitohs have their own injury concerns with full-back Alex Johnston (hamstring) and Sam Burgess (glute) forced off before half time.

South Sydney's seventh win from 11 games keeps them in touch with the NRL leaders, while the Cowboys' eighth defeat surely ends their finals hopes.

Cowboys coach Paul Green said scans on Sunday would confirm whether or not Scott had suffered a medial ligament injury.

Scott went down with anterior cruciate damage to his other knee in week two of the 2017 campaign, ending his season, and Green is relieved this time it doesn't look as serious.

"Hopefully, it's not too bad," he said.

"They're saying medial ligament. It's not the knee he did last year so hopefully it's not too bad."

Scott's Queensland team-mate, Souths' skipper Greg Inglis, is also keeping his fingers crossed the prop will not miss a second straight Origin series.

"Thumper and I are really good mates, best mates," Inglis said.

"When I saw him go down I was praying it wasn't an ACL. Fingers crossed it's not too serious and he's not out for too long."

Rabbitohs coach Anthony Seibold had no doubt the game-deciding penalty was a correct call.

"Renner had to go to his left boot to kick the goal so he didn't get a fair opportunity to kick," he said.

Australian Associated Press