How much balance is too much? This much: at exactly halfway through their innings at Lord's on Sunday, South Africa were exactly halfway through their chase to beat Bangladesh in their T20 World Cup match.

That the South Africans required a modest 118 to win mattered less than the fact that they needed to score quickly to hike their sagging net runrate to be confident of staying in the running for a place in the semifinals.

Because, if India beat Australia in the day's second match, NRR would decide who would join the nearly-qualified Aussies in the semis: South Africa or India. Considering, going into Sunday's games, South Africa's NRR was 0.734 and India's 2.268 - as many as 1.534 degrees of difference - maybe it never was about that equation. India were probably too far ahead for the South Africans to reel them in. But that doesn't mean the NRR situation should be ignored.

Besides, had South Africa taken better care of their NRR earlier in the tournament they would have been on more level terms with the Indians. Had they not been bowled out for 107 chasing 173 in a dismal display against Australia, for instance. Or losing eight wickets and taking all of 16.5 overs to chase 127 to win against Pakistan.

So, on Sunday, when Dane van Niekerk missed a reverse sweep to Sanjida Akter's last ball of the 10th and was trapped plumb in front, reducing South Africa to 59/3, the chase was so balanced that the Proteas' campaign seemed in danger of toppling into the abyss.

Then the South Africans dared to step still closer to the edge by losing Annerie Dercksen, Marizanne Kapp and Nadine de Klerk a scant 26 runs and 29 deliveries apart. They reached the last over in search of five. Chloe Tryon edged four of them into the scorebook off Marufa Akter's first effort, and sealed it next ball with a chipped single that blooped marginally over the cover field.

"That sums up South Africa's performance," Ian Smith said on commentary, "They've done just enough to win."

Indeed. Kapp exploited the significant swing on offer like the champion she is for her figures of 1/9 and was run out for 16 thanks to De Klerk's midpitch hesitation. That made her the obvious choice for the player-of-the-match award. But when she collected her prize from the host broadcaster she said, "Ugh, I want to give this back after our batting innings. We seem to always do this. I don't know why. But we'll take the win. A win is a win, especially at a World Cup, even though it was very scrappy."

Laura Wolvaardt was asked, at a press conference directly after the match, whether she could explain this strange and worrying phenomenon. "No, not quite," Wolvaardt said. "Today we needed a win and it's frustrating how we got ourselves into that position. But we won the game, we got our points and now we sit and watch the next game.

"Maybe it was a mindset thing today. I think knowing that we only needed to chase [118], we maybe batted within ourselves and didn't go to our positive options early enough. In situations like that we've got to take the braver option earlier.

While still on the field, Wolvaardt had said: "I never thought I'd be supporting the Aussies, but go Aussies!"

Indeed again. Because an Australia win would knock India out of the final four. But most teams aren't good at staying focused when the result doesn't matter, particularly in tournaments. With the South Africans looking on and more glum every time the television cameras panned to them, the Aussies flopped in the field, where they lacked energy and dropped four catches. But they held it together well enough at the crease to win by six wickets with an over unspent.

When the Australians needed nine off 13, the cameras caught Kapp beaming a broad smile. With four required off 11, Van Niekerk popped up; also a picture of happiness, complete with a thumbs-up.

South Africa made the semis for the fourth time in as many editions of the competition. You could argue they didn't deserve to get there - their only convincing performance was against India, when they chased 159 to win by four wickets with five balls to spare. Even the Netherlands gave them trouble, reaching 100/1 in the 14th before they lost seven wickets for 20 runs.

And here they are, still alive and still kicking. Unbeaten England will make massive opponents in the semifinal at the Oval on Thursday, but who's to say - on balance, having come this far - that South Africa won't do just enough? Because, as they've proven, you don't need to be emphatic. You just need to win.