McLaren was preferred to Wayne Parnell as Kallis's successor in the all-rounder role, to win his second cap, four years after his first.
But the 31-year-old left-handed batsman and right-arm bowler made it clear he was not about to take up the mantle of one of the game's greatest all-rounders.
"Let's get it right straight away and you can all save yourselves some typing," he told reporters at a news conference at SuperSport Park after Australia had finished on 297 for four.
"I am no Jacques Kallis. I wouldn't even pretend to be walking in his shoes. There is no comparison between the two of us."
"For me it is first a case of stepping up into the role, and to try and make use of the opportunity as best I can."
McLaren, who took a wicket in his first spell and finished the day with figures for 1-53 off 16 overs, said he saw his role as a hard "grafter", to hold up an end when bowling and to bat as efficiently as he could in the number seven position.
"It will be a work in progress," he added.
The 38-year-old Kallis retired after South Africa's series win over India in December, scoring a century in his final knock to go into third place in the all-time list of run scorers.
ALSO SEE: South Africa vs Australia, 1st Test