With a Test average of 46.60, Jacques Kallis is a key player for South Africa. Everyone knows it, not least Glenn McGrath, who before this series broke with convention and publicly announced two targets: Kallis and Gary Kirsten. And as ever, he has been as good as his word, dismissing one of them in each of South Africa's innings so far. In this series McGrath has bowled 29 balls to Kallis, conceded 10 runs, and dismissed him twice. Kallis's average of five is less than a ninth of his career average.

McGrath only knows one method, and it doesn't involve experimentation. Today his performance was, well, metronomic: he bowled 19 balls to Kallis, and every single one of them pitched in the corridor outside off.

McGrath's trick is not to make the batsman always play - Kallis was able to leave 37% of his deliveries today (7 out of 19) - but to make any attacking stroke fraught with uncertainty. Kallis scored six runs today; two singles and one four when McGrath sent down a rare half-volley.

Kallis was in control of 84% of his shots off McGrath, but McGrath's relentlessness is akin to Chinese torture, and invariably the batsman will crack, as Kallis did today when McGrath straightened one and found the edge.

Since the second Test at Lord's last summer, McGrath has had 78% of his victims (45 of out 58) caught, most of them in the cordon. He doesn't swing it, he's no more than fast-medium, but McGrath continues to be too good for the world's best batsmen.

Rob Smyth is on the staff of Wisden.com.

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