He drifted across field, sending Brenko Lee inside, who popped it to Josh Jackson for the Bulldogs' go-ahead try to make it 14-9 in the 63rd minute.
Coach Des Hasler looks set to shuffle No7 Moses Mbye between the halves and hooker, after back-up playmaker Matt Frawley was brought on in the 25th minute and combined beautifully with Reynolds.
It also raises questions about No9 Michael Lichaa's future, after he spent the final 55 minutes on the bench.
Reynolds didn't have it all his own way, however.
Souths fullback Alex Johnston scored the opening try when he burned the Bulldogs No6 for speed to run 55m and cross in the corner.
But Reynolds' reply was swift and five minutes later he grubbered for the in-goal and when Johnston let the ball bounce, he snuck under the Rabbitohs No1's guard to ground it inches from the dead-ball line.
It appeared the teams would go in to the sheds locked at 8-8, however, when Dogs skipper James Graham threw it over the sideline from the kick-off, Adam Reynolds booted a field goal from the ensuing scrum to give Souths a 9-8 lead.
After Jackson's try, the momentum was with the Bulldogs with Kerrod Holland and Josh Morris running in tries in the final 14 minutes as Canterbury cruised home.
Souths captain Sam Burgess will have a nervous wait on his hand after being penalised for a shoulder charge on Greg Eastwood and is in danger of missing next week's clash with Brisbane.
His brother George could also be in hot water after appearing to throw an elbow at Aiden Tolman late in the game, just a week after returning from a two-week suspension for a similar offence.
- AAP