He was one of the first to congratulate and embrace Merritt after the winger put his Origin travails behind him to score a try in the 59th minute.
Further tries to centres Bryson Goodwin and Dylan Walker rounded off a comprehensive Rabbitohs' display.
Canberra's away record for the season slumped to 1-8, as they failed to capitalise on a good start.
Things looked to be going the visitors' way when Jarrod Croker kicked a fifth-minute penalty to open the scoring and Souths appeared to have a perfectly good try to Goodwin rubbed out for a forward pass.
Canberra had winger Sami Sauiluma placed on report for a shoulder charge on Jeff Lima in the first half and failed to take advantage of some pressure early in the second.
South Sydney 32 (S Burgess, B Goodwin, J Hunt, I Luke, N Merritt, D Walker tries; A Reynolds 3, B Goodwin goals) bt Canberra 2 (J Croker goal) at ANZ Stadium. Referees: Ben Cummins, Chris James.
- AAP