Kallis has been the rock of South African teams since 1995. He averages 55.21, has hit 44 centuries, more than anyone other than Sachin Tendulkar, and is fourth highest all-time runmaker.
He has been a true colossus of the game and there has long been a plan to keep arguably the game's finest allrounder ticking over until the 2015 World Cup.
He sits out some limited-overs series. Cricket South Africa know his value to them and want to prolong his career, certainly until then as they strive for their first World Cup crown.
However, there are signs of cracks. He needs to perform.
This year the big man from Cape Town has scored 160 test runs in 10 innings at 16.0. Just two half centuries in that time.
Kallis needs big runs for two reasons; one to reassure himself and secondly to reassure his team, and selectors, that he's still worth his place.
Deciding when time is up is a tricky, emotional business. There's a reputation to consider.
No outstanding sportsperson wants to sully their standing, and their record. Yet taking the step away can be desperately hard.
This week, Olympic champion sculler Nathan Cohen did just that.
He'd been pondering his future for some time. His was no kneejerk decision.
But he knows he reached the mountaintop at Eton Dorney last year. Time to do something else with his life. He is 27.
Australian tennis legend Ken Rosewall chugged the world's baselines for 20 years, chasing the Wimbledon dream. He was a true great, with eight Grand Slam titles but one notable hole on his resume. He had been Wimbledon runnerup three times.
At 39 he made the final final once more. He was the overwhelming sentimental favourite.
Result? Rosewall was chewed up by the brash, crass 21-year-old American Jimmy Connors, 6-1, 6-1, 6-4. Connors then bashed Rosewall 6-1, 6-0, 6-1 a couple of months later in the US Open final for good measure. End of the road.
In the coming days, Kallis may prove the doubters don't know what they're on about. In which case South African cricket will breathe just a little easier, at least for the time being.