Canberra took a giant leap towards the NRL finals with a 40-25 win over South Sydney but another two season-ending injuries dropped their stock of fit players to a critical level.

The Raiders went into halftime 19-6 down at ANZ Stadium before piling on six tries in the second half to complete a remarkable turnaround and continue their push towards an unlikely top four finish.

They moved to 28 competition points, just one behind fifth-placed Brisbane and two behind the Sydney Roosters, to leave them in a strong position with their remaining two games against bottom sides North Queensland and the Bulldogs.

But the win came at a heavy cost, with halfback Marc Herbert (medial ligament) and prop Troy Thompson (achilles) both suffering season-ending injuries.

It means the Raiders' first-grade squad has now shrunk to just 17 players heading into the business end of the season with the pair joining the likes of William Zillman (knee), Glen Turner (ankle), Lincoln Withers (knee), Michael Weyman (groin) and Tom Learoyd-Lahrs (suspension) on the sidelines.

"Our injury tally this year is unbelievable," said five-eighth Terry Campese, who continued his rich vein of form in the win.

"You come off the field thinking, 'who's injured this week?'

"Having our starting halfback and starting front rower with the injuries they've got it's disappointing after the good comeback we had today."

The injury woes leave coach Neil Henry with plenty to ponder ahead of Saturday's clash with the Cowboys.

The Raiders are short on halves, with Herbert taking over from disgraced star Todd Carney, and Henry could be forced to switch lock Alan Tongue into six or seven.

"It's one of our options, we'll just have to have a look," Henry said.

"We were down to 19 (fit players) before today ... so now we're down to 17.

"We might look at the NYC (under 20s) team, we'll pluck someone from somewhere."

Campese backed whoever was chosen to step up to the mark.

"Whoever has come in this year has played awesome and I suppose whoever replaces Thommo and Herbie will get the job done too," he said.

Souths halfback Chris Sandow's 40m field goal on the stroke of halftime gave the Rabbitohs what looked to be a handy 13-point advantage at the break.

But the Raiders came out a different side after the interval, hitting back just two minutes into the half through prop Joe Picker.

Souths-bound centre Colin Best then scored the pick of the tries five minutes later with a superb solo effort from halfway and Adrian Purtell scored his second of the day to reclaim the lead with 23 minutes to go.

The Raiders didn't let up, with Brett Kelly, David Milne and Joel Monaghan all scoring runaway efforts to cap an impressive team performance.

"I think it shows the character of the side," Henry said of the comeback.

"We talked about it at halftime we obviously needed to play a lot better football and dig in a bit, and we did that."

Souths looked good in the first half but could not capitalise as they did in last week's shock win over Manly.

"Overall I was happy with the performance... but there was probably a little too much to play for Canberra today," Rabbitohs coach Jason Taylor said.

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