Three matches, four teams, 44 players, four captains: the semi-finals of the World Cup. These are the best games to win and, by a distance, the worst games to lose. The long slog is over, the sprint to the finish is about holding your nerve. Having come this far, the final is but an innings, an over, or a catch away. Blow it and the pain lives with you always. Nail it and the big day out is yours forever.

Each captain must pitch it just right: neither too desperate, nor too chilled. MS Dhoni is a master of this. For him, the greatest demand was in India four years ago, when a nation hung upon his every word and step. He is the great diffuser of pressure, ignoring the big- picture questions thrown at him and instead blinding everyone with rhetoric that means very little but satisfies very many.

Dhoni is less concerned with result than process. He had Sachin Tendulkar in his team but expected little from him, preferring to talk about the need for the others to be relaxed and ready but not dependent on a man whose life had been lived with the weight of unreasonable expectation upon his shoulders. Maybe Dhoni agrees with Gilbert Jessop: "Don't give advice to a batsman going in. If he's inexperienced, it will only make him nervous; if he's an old hand, it is generally unnecessary. Give him credit and opportunity to use his own judgement. If he doesn't do so at first, he soon will."

Whether or not Dhoni has an analytical eye for the game is open to question. He appears to set a tone rather than a plan. For sure, one-day cricket gets his juices flowing but perhaps this is because the limited-overs format dictates his moves. Dhoni is more responder than creator, a man who backs instinct and talent over analysis and words.

Sensing the danger of the long run chase against Muttiah Muralitharan in the final against Sri Lanka in Mumbai, and after the loss of both Virender Sehwag and Tendulkar, he promoted himself to No. 5. Gary Kirsten, then the Indian coach, says that the captain turned to him just before Virat Kohli was dismissed and said: "Shall I go?" The look in his eye and the energy bursting from his strong features were enough for Kirsten, who smiled and nodded in the affirmative. "A no-brainer," remembers Kirsten. "He was going to go however I reacted, but confirmation was useful support to his belief that he could do it on his own. As he left the dressing room, I sort of thought that was it, that we would win."

"Clarke's biggest hurdle may well be the team's pervasive sense of over-confidence. It is one thing to play without fear, quite another to play without reference to a threat"

Dhoni played Murali beautifully, picking him off with the sort of calm assurance that has hallmarked his career. When he struck the winning six, he might as well have been Jessop, so long and straight did it fly. He had barely made a run in the tournament but that day he finished unbeaten on 91, an innings to rank alongside any in the history of the World Cup.

It is this self-assurance that sets him apart and inspires those around him. The animated celebration of the catch, low to his left, against Bangladesh in the quarter-final the other day reminded the world of his commitment to the job at hand. His bowlers are on song, his batsmen capable of exceptional innings. The confrontational attitude prevalent in modern India ripples through the team. Australia had it easy in the recent tri-series. It will be a very different India that comes to play in Sydney on Thursday.

Michael Clarke is acutely aware of this. Indeed, nobody may be more aware. Some in his team say that India can't beat them. Clarke knows different. In many ways, Clarke and Dhoni are polar opposites. In others, they are remarkably similar - two singular men, at once aloof and yet personable. Both thrive on the drug of power and its offshoot of responsibility. Away from the game they like a bit of bling and bike; come the toss, they are driven by practicalities. Clarke is the greater tactician, creating moments and opportunities with his savvy field placements and smart switches of bowler. He hates a game that treads water and so pushes it along with aggressive moves and, if necessary, sacrifices.

He too has found his best team in the nick of time. These days Shane Watson is twice the cricketer when the situation of the game is set for him, thus he is better batting lower down and bowling when the slog is on. If Watson has time to think, self-absorption can take over. Watson is at his best when Clarke does the thinking for him.

Josh Hazlewood must surely take the new ball, allowing Clarke the attacking option for longer. Here the two new balls work in favour of the Australians, who have five seamers to the three sure to be chosen by India and South Africa. Against this, Clarke has less flexibility with spin and may have to use himself in the mid-innings holding pattern, especially if the SCG pitch is as flat as the one the Aussies were given for the Sri Lanka match.

MS Dhoni congratulates his team-mates after sealing the win Associated Press

It appears that Clarke has won over his team. Perversely, they have admired his sheer bloody-mindedness to become ready for the tournament. This has shown them how much the game means to him and allows them to wallow in the same outward show of nationalism. But it is a fragile relationship, exaggerated by the presence of the ever-popular George Bailey. Clarke needs runs otherwise the mean-spirited continue to point fingers at him. How wrong that a man driven by the desire to succeed, a man whose heart is wedged deep into Australian cricket, should still be so questioned.

But Clarke's biggest hurdle may well be the team's pervasive sense of over-confidence. Empowered by bravado after an all-conquering summer, the balance between intimidation and a fall is more acute than the players might know. It is one thing to play without fear, quite another to play without reference to a threat. If we take Glenn Maxwell as the barometer of an Australian state of mind, the risks attached to it cannot be ignored.

But, but but... there is another battle to be won first. A battle of cricketers that means so much to rugby-playing peoples. Is AB de Villiers able to do what Francois Pienaar once did and lift a trophy on behalf of the Rainbow Nation? His aching desire is plain to see and almost painful to hear. A man can want something too much. His public pronouncements have been extraordinary. His private fears may be evident in them.

The great thing about the win against Sri Lanka in the quarter-final was that it came in the way de Villiers had told us it could: the best cricketers playing the best cricket and giving not the merest whiff of vulnerability to the enemy. It is true that de Villiers must persuade the South Africans to continue to attack, but first he must persuade himself. Oddly, it is not the natural South African way. Reticence invades the collective mind. Almost certainly, this comes from a lack of ego. It is the stark difference between South African and Australian sportsmen.

Somehow the captain must get into the head of each of his men and convince them that it's all right to give it a full go; it is okay to show off, boys, okay to parade your gifts. You have one shot at it, de Villiers must say, don't waste the bullet. He could encourage Dale Steyn to bowl with a slip at all times - even late in the innings - if only to make him see the value of a wicket. Morne Morkel should be urged to bowl fast and nasty, never mind economically. Imran Tahir must keep spinning that ball and, come to think of it, so must JP Duminy. Those are short boundaries at Auckland's Eden Park and Brendon McCullum's men will be under instruction to clear them. Spin the ball, lads, and turn the rope-clearing into a risk.

The moment has come for South Africa to rid themselves of the past - of curses and quotas and chokes and lingering great question marks - and make it to Melbourne with free minds and passionate, unified hearts. Once there, the job will be a whole lot easier. As Jack Nicklaus said about winning 18 Majors: "The first one is the hard one, after that it's easy." Nice call, Jack.

And finally to McCullum, who deserves the many accolades bestowed upon him of late. His team plays cricket exactly as it should be played. These men define the game's spirit and play it with a craft that belies that country's affection for the larger oval ball.

"Perhaps the secret of McCullum is that he really does play the game without an iota of concern for the consequence"

I wrote recently of McCullum's bold interpretation of cricket. Essentially he is urging his men to perform as if the opposition are nothing more than an unavoidable part of the script or piece of the canvas. He believes in expression as, say, a director of theatre or a painter might believe in an expressionist form of his art.

McCullum is saying, we have a talent, a stage and an audience. Go show them that we can do it. This is the point de Villiers wants to make but does not quite know how.

In the slugfest that was the Pool A match between New Zealand and Australia, McCullum's team did exactly this, shocking everyone - not least the Australians - with their complete disregard for the opponent. It was not until Mitchell Starc woke up that the game changed course. New Zealand just about held their nerve, though McCullum would not want to bank on Kane Williamson playing a shot of such audacity and brilliance in a semi-final situation. Or perhaps he would? Perhaps that is the secret of McCullum, that he really does play the game without an iota of concern for the consequence.

What a way to be! The contrasts between McCullum and de Villiers are riveting. There are similarities too, which are driven by modesty, manners and a glowing respect for the game. And there is their own outrageous batsmanship - an innings from either can transform any match. But I have a hunch it is the differences in them that will shape the match. Who will get the most from his ethos? And thus, from his players? Which of them will do as no other New Zealander or South African has done before?

These semi-finals promise to be the matches of the tournament. Perhaps even matches for all time. The contrast and the connections between the opposing captains is one of the attractions. Which of them can best cope when the stakes are so high?