It was meant to be the final chapter of the Mark Gasnier versus Greg Inglis story.

Instead, 20-year-old South Sydney centre Dylan Farrell stole the show with the third hat-trick of his fledgling career in his side's amazing 34-24 comeback victory at WIN Stadium.

Farrell famously bagged his first hat-trick in his debut match to clinch victory over the Wests Tigers at ANZ Stadium last year.

As Rabbitohs coach John Lang said on Sunday, he knows how to get over the line.

"We've got a good attacking team and we've got some players who are really good with the ball so if I run the right line I'll just be there in support, it pays off," Farrell said.

NSW star Gasnier, who will retire at season's end, was marking up on Queensland rival Inglis for the last time and had the better of the Souths centre with a hand in the Dragons' first three tries as they skipped to a 20-0 lead.

Two of those had come as he linked with Farrell's opposite number Matt Cooper, who bagged a double.

It looked like a case of the big boys showing how it was done.

Enter Farrell, who scored two from Chris Sandow kicks and the match-winning third in the 77th minute as Souths stunned the home fans.

"The first 18 minutes they just got a quick roll-on but we knew we were in the game," Farrell said.

"Halftime was pretty relaxed, even though we were down 20-6 we were all relaxed because we knew we could get back into it, we just had to run harder, tackle harder and we did in the end."

Souths coach John Lang said Farrell had taken a huge responsibility on at a young age in 2011.

"He's probably been catapulted into playing regular first grade maybe a little bit before his time," Lang said.

"He's had a big load to carry, to be perfectly honest, for a young guy, a lot of responsibility.

"At times he's struggled with it, mostly he's done a good job so he's carried a big burden for us for such an inexperienced player.

"He knows his way to the line, Dylan, that's one thing. If he gets a half chance he doesn't mess too many up."

"(The last try) That's classic Dylan, if he gets half a chance he'll get it over."

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