They say that the IPL is where successful World T20 teams are created. They look at West Indies, as shambolic a national set-up as you could imagine, but see only the World Boss and his Merry Men, megastars throughout their adopted land, and "Champion" dancing their way to a Wankhede semi-final.

They look at England, who've spent a decade looking the other way but have finally been won over by the merit of overseas franchise leagues. And those same leagues may now, in turn, be looking to the free-spirited exploits of Joe Root, Ben Stokes, Jason Roy et al, and seeing them as auditions for future auctions.

They look at Virat Kohli's unconscionable finishing skills, perfectly honed at Royal Challengers Bangalore's finishing school. They look at Steven Smith's preposterous repertoire, including flicks to leg from off-side wides, and presume it can't be long, surely, before Australia finally gets its act together in this competition.

But then they look to South Africa, and what do they see? A somewhat watered-down soup of talent and expectation, for whom the prospects of a major global trophy seem thinner than ever before. And, far from enhancing their chances of breaking that duck, the IPL may well be the tournament in which they drowned their golden goose.

In particular, one match may well have drowned it. One innings in fact, the legacy of which goes some way to explaining why 16,553 people ignored the dead-rubber status of South Africa versus Sri Lanka on a Monday night in Delhi to sit in the stands and chant the name of a batsman who averages 23.58 in 71 T20Is, and whose highest score in the format is 79 not out.

It was at the Chinnaswamy Stadium on May 6, 2012, while playing for RCB against Deccan Chargers, that AB de Villiers torched the 20-over reputation of his South Africa team-mate, the greatest fast bowler of his generation. Twenty-three runs were tenderised from Dale Steyn's final over of the night, including an inside-out swing for six over extra cover that has to have been seen to be believed.

But Steyn wasn't the only one to go into orbit that night. De Villiers himself was propelled into a galaxy that only Chris Gayle, among overseas stars, can truly know, and the effects of that new gravitational pull have been felt ever more acutely by South Africa with each passing year. The issue of AB's workload, and the "will he or won't he?" questions about his international future were a permanent accompaniment to England's recent Test tour. Though he's committed for now, with the Test captaincy providing a new anchor, it doesn't change the feeling that something rather terminal took place in Delhi on Monday evening.

Two decades of opportunity at ICC tournaments have drifted away for South Africa. The teams of Pollock and Boucher, and Smith and Kallis, have long since come and gone. On this night, one got the impression that the team of Steyn and de Villiers was taking its last stand too. They achieved an empty victory against an even more eviscerated Sri Lanka, and South Africa captain Faf du Plessis rightly found little to cheer in the aftermath.

"The sad thing is that it's now four years to the next [T20] World Cup - it's not just two," he said. "A few players here won't be there then." He went on to add that "hopefully we can see a bit more of AB going forward" but deferred questions about Steyn's future to the man himself. "He looks hungry still," du Plessis claimed. But not hungry enough to have insisted, as Chris Morris apparently did against Afghanistan, that he was the man for the moment.

You wonder if Steyn truly believes he's the man for any moment in white-ball cricket these days. When Mohammad Shahzad, Afghanistan's roundhouse slugger of an opener, swiped him out of the Wankhede last week with the damning assertion that "Dale Steyn is not dangerous", he was merely responding to the evidence of his opening over of the tournament - another 23-run pounding, this time at the hands of England's Roy and Alex Hales in their record-breaking run-chase. And du Plessis's equivocal response on that occasion did little to inspire confidence either.

At last, Steyn bagged his first wicket of the tournament. Though Steyn responded with his trademark chainsaw punch, the more telling reaction came from Steyn's captain. Up du Plessis trotted with a massive, heartfelt bear-hug - not your standard greeting at 96 for 7

In fact, it would be hard to contend that, in limited-overs cricket, Steyn has been himself - his true late-swinging, block-knocking, pole-plucking self - for several years now. When Grant Elliott hauled him off the floor in Auckland this time last year, after striking the most famous six in New Zealand's international history, the look on Steyn's face was that of a man who once had all the answers but was now struggling even to pinpoint the question.

And Monday night, in one of the most facile victories that you could ever hope to complete at a world event - a victory sealed with a de Villiers smear for six that gave the crowd the money shot they had been baying for - Steyn was South Africa's odd man out, the legend reduced to an afterthought.

At first, all the old mechanics seemed to be in good working order - the pitter-patter approach to the crease, the arc of the arms, the coiled-spring whip of the shoulders - and his first four balls were fast and true, with a hint of swing and zip off the deck. But then he strayed in line to be picked off through fine leg, and something died in his intensity.

Tillakaratne Dilshan was ready and waiting next over: no need for a sighter, out came the Dilscoop, very first ball. Steyn turned on his heel and was marching back to his mark before the ball could reach the boundary. His fourth ball was too short, and not sharp enough either. It elicited a hurried pull from Dinesh Chandimal, but only out of respect, you suspect. David Miller, five yards in from the rope, could only watch as it sailed over square leg.

By the fifth ball of the over, Chandimal was in his hitting zone. He flung his front leg open to clear de Villiers, on the edge of the circle, with a violent mow through mid-on. Sixteen runs had been pounded from the over, as Steyn - in South Africa's final match of the tournament - finally completed the analysis, 4-0-55-0, that had been so rudely interrupted in that opening fixture at the Wankhede.

At the end of his opening burst, Sri Lanka had bounded along to 30 for 0 in three overs. By the start of his third over, their innings was in freefall at 89 for 6 and lesser cricketers had made the task seem child's play.

Aaron Phangiso, better known in the build-up to the tournament for being a cause célèbre rather than a cricketer, struck twice in his first over after being bashed for ten runs from his first two balls. Farhaan Behardien, with two overs and one wicket in 24 previous T20Is, then dobbled Shehan Jayasuriya and the main man Dilshan before he had even doubled his overs tally.

And then, never one to be overlooked for long, up rocked Imran Tahir to bowl Chamara Kapugedera through the gate and set off on another of his solipsistic victory parades. As he cavorted to the edge of the 30-yard circle with arms aloft, glory in his heart and his team-mates nowhere to be seen, his inability to see the futility of his achievement was strangely affecting.

But at least the stage was set for Steyn to sweep back into the contest and mop up the dregs of Sri Lanka's resistance. Instead, Thisara Perera was waiting for him, as if armed with a sock full of sand. Tonk! His first ball, outside off, was butchered for a one-bounce four straight back whence it came.

Steyn's follow-ups were fierce, as you'd expect from a living legend, but the damage to his dignity had been done.

At last, from the final ball of his third over, he bagged his first wicket of the tournament as Perera wellied a short ball to Behardien at cover. Though Steyn responded with his trademark chainsaw punch, the gesture seemed perfunctory, not pronounced. The turf cowered for impact as his shoulder wound into the blow, only for the thunder in his down-stroke to give way to a dismissive wave of the hand.

The more telling reaction came from Steyn's captain. Up du Plessis trotted with a massive, heartfelt bear-hug - not your standard greeting at 96 for 7. But then, six balls later, we learned the subtext of the gesture, not to mention the whispered words that the cameras could not pick up. "Well done, mate, take a blow …"

Back came Behardien, he of four overs in 25 T20Is, to continue a spell of dibble-dobble that the greatest fast bowler of his generation had so rudely interrupted. This time he was tonked back over his head for six by Dasun Shanaka, but at 2 for 15 in three overs, his figures barely noticed the scratch.

Next to take the stage was Kyle Abbott, Steyn's skiddy seam-alike, who responded to the call with a Steyn-alike swinger that grazed the edge of the left-handed Rangana Herath. Steyn steamed in for one final time, summoning the fury to give Jeffrey Vandersay the hurry-up, but a flustered final-ball bouncer lobbed cruelly into space.

Instead it was Abbott who produced another trademark Steyn dismissal - the one that held its line as it angled back in, before bursting off the pitch to flatten Vandersay's stump cam. One ball later, those wires were out of the ground again as Suranga Lakmal's suicide single was cut short by David Wiese's shy from point.

Sri Lanka were all out for 120 in a contest as anonymous as South Africa's overall campaign. But the crowd knew what they had come for. "AB! AB!" chanted the Feroz Shah Kotla as a truly great bowler slipped into the night for surely the final time in a major global event.

"I don't think he's even thinking of retiring from any format," said du Plessis afterwards. "Dale Steyn is still there for us."

But it didn't look that way on this night. It hasn't looked that way for months.

Andrew Miller is UK editor of ESPNcricinfo. He tweets @miller_cricket