"Every game is different, teams are different and the situation is different," Bellamy said.
"They are the premiers and they're not that for no reason."
At this time last year, the Storm had 10 competition points compared to 12 this season.
That gave him confidence heading into the Origin period, when the Storm will supply four star players - Cameron Smith, Billy Slater, Cooper Cronk and Will Chambers - to the Queensland team.
"Last year we were a fair way down the pack going into Origin," Bellamy said. "We are certainly playing better; defence is probably the main area and I feel a bit more confidence in it going into this period.
"The effort over most of the nine rounds has been really good and we will need that tomorrow night."
Fullback Slater made a blistering return from a shoulder injury in the Storm's last outing, scoring two tries in their win over Parramatta.
While they will soon be Maroons teammates, the battle between Slater and Souths fullback Greg Inglis, who started his career in Melbourne, will be key to the match.
"I'm sure Billy will be keen to play well after missing a month and will be keen to get another game under his belt before Origin," Bellamy said.
The Storm were dealt a blow on the eve of the Rabbitohs clash when young prop Jordan McLean was ruled out for at least a month with a hamstring injury.
— AAP