Kallis feasts on the green grass of home
Petersen admitted that South Africa were "surprised" that Sri Lanka asked them to bat, on a pitch that looked "quite dry". At first, they may have suspected a poisoned apple but no such dangerous food emerged. All that lay before them was a land of milk and honey: batting paradise with the chance for the two at the crease to prove their differing, but equally important, points.
Petersen's need to make a statement is obvious. He has just been recalled to the national team after being dropped, for no real doing of his own, but the hard-to-ignore form of another - Jacques Rudolph. If there was any glaring fault in Petersen's previous nine Tests it would be that he failed to notch up milestones often enough. His century on his debut Test was memorable but fifties against West Indies and Pakistan were achieved against forgettable, below-par opposition or in equally forgettable batting-friendly circumstances.
His last series, against India, was characterised by difficult opening partnerships, on both sides, as the hosts prepared seamer-friendly pitches as part of a ploy against the sub-continental side. He was dropped, despite managing 77 in the first Test, because Rudolph was the popular choice, having made a stirring comeback to South African cricket.
Petersen always knew that if he continued grinding away at the domestic scene, the pendulum would have to swing back in his favour. "I always believed I had the chance to get back and I had a few good performances at domestic level," he said. "I always believed I could do it. It all depended on me getting runs on the board." Since being dropped, he has scored three first-class hundreds, showing his patience, maturity and composure and forcing his way back into the national team.
Even that was not enough for vindication. Like Ashwell Prince, who scored a century in the opening position in 2009, Petersen had to be able to show that he was good enough, not just anywhere but in an international match. He realised the value of a big score and adopted the same attitude as he has had in domestic matches this season to get there: the wait, watch and then stealthily attack. "A hundred is a big milestone and it was quite satisfying to get to that," he said. "In other games, I got to 30 and 40 and I was a bit disappointed. For me, it's about pushing the bar and would have liked to have scored more."
It was an innings that could be remembered as being a turning point in Petersen's career because it has likely bought him time and flights to New Zealand and England next year. South Africa's opening pair has long been a conundrum but Petersen appears to have solved that, with the help of the opportunities he was fed by the Sri Lankan bowlers.
Kallis is on the opposite end of the spectrum. After 150 Test matches, some may think Kallis has nothing left to achieve. They would be wrong. Before today, he had not scored a century against Sri Lanka, the only Test playing nation he had not managed three figures against. Perhaps more fresh in his mind was the pair he suffered last week at Kingsmead, something that was foreign to Kallis, who had gone 16 years in international cricket without ever enduring a duck in both innings.
Combine those two factors with Kallis' age and the need for him to come good emerges. He is now 36 years-old - not yet old enough to be hard of hearing - so would have picked up the whispers in the wind that are suggesting he is getting on and that team management should start considering his future. His recent vulnerability against the short ball, particularly against Patrick Cummins, highlighted those very things Kallis would have wanted to remain in the dark: signs of age.
He had three forgettable innings against Sri Lanka and would have had a fourth, if Chanaka Welegedera had caught his top-edged pull. At that stage, Kallis was on just one. But, like Kumar Sangakkara in the last match, he showed Sri Lanka what happens when you give one of the world's best players a second chance and went on to record a magnificent 150, in perfect symbolism with his 150th match.
As the run machine rolled on, Sri Lanka continued to pepper Kallis with short balls. "We were surprised at the lines and lengths bowled," said Petersen. By then, Kallis had adjusted to keeping the pull down and went on to record one of his classiest knocks. In the process, Kallis owns Newlands the way Mahela Jayawardene does the SSC in Colombo and Graham Gooch did Lord's. He passed 2,000 runs on his home ground, a sign that the grass really is greener for some at Newlands.
Firdose Moonda is ESPNcricinfo's South Africa correspondent