Not long ago, Zaheer Khan was seen as someone who was symptomatic of the ills that plagued Indian cricket: he was accused of being unfit, not having enough hunger and drive, and not capable of rising to the big occasion.
Fast forward to the present, though, and plenty has changed. In the series against New Zealand, Zaheer was the go-to man for MS Dhoni - he bowled 115.3 overs in the three Tests, much more than Ishant Sharma (94.2) and Munaf Patel (84), the two other specialist seamers in the Indian team. His series average of 30.76 wasn't outstanding, but he bowled much better than the numbers suggest, beating the bat regularly and repeatedly asking questions of New Zealand's top order. Of the13 wickets he took in the series, 12 were of top-order batsmen. (Tim Southee, in the first innings of the third Test, was his only lower-order victim.)
Breaking up Zaheer's career into two halves, it's easy to see that he's become far more potent since he came back into the Indian team for the tour of South Africa in December 2006. His average since that comeback is 30.43, which, again, doesn't do justice to how he has bowled, but it's still significantly better than his average before that tour. His strike-rate has improved by 10 deliveries per wicket, and he has taken more five-fors in 23 Tests since than he had in 42 games during the first phase.
The haul of 13 wickets in New Zealand also left Zaheer with a tally of 149 overseas wickets, which is third among all Indians, after Kapil Dev and Anil Kumble. Even more significantly, it turns out that Zaheer has the best away average among all Indian bowlers who have taken at least 75 wickets overseas. His average of 32.03 is better than that of Kapil (32.85) and Javagal Srinath (33.76), the two other Indian fast bowlers who've made a mark around the world in the last 30 years.
In that sense, Zaheer's numbers suggest he is a departure from the typical Indian fast bowler of the past, who was more at home bowling on the uneven pitches of India than on true surfaces abroad. Kapil and Srinath both did much better at home, though you'd think that conditions overseas would suit their bowling more; Kapil averaged 39.18 in England and 42.13 in New Zealand, while Srinath averaged 39.36 in England and 50.70 in Australia. Zaheer, on the other hand, has generally relished bowling outside India - he averages 29.27 in England and 22.95 New Zealand; in India, the average balloons to 38.14.
Admittedly, Zaheer has played almost two thirds of his Tests away from India, but he has also made them count, taking 149 of his 210 wickets on away soil. His percentage of 70.95 is the highest among all bowlers who've taken at least 200 wickets. In fact he is well clear of second-placed Michael Holding, who has a percentage of 65.46. Daniel Vettori makes it into the top 10 as well, which is an indication of how unresponsive in New Zealand are for spinners.
The two tables below suggest that the biggest difference over the last two-and-a-half years has been the way he has bowled to right-handers. In the first six years of his career Zaheer was more effective against left-handers, averaging 33.32 against them at a strike-rate of less than 60; against the right-handers his average was 37. (These numbers exclude the matches he played before June 2001.)
More recently, though, Zaheer has added the indipper to the right-hander to his armoury, and that has made him far more potent against them, with the average coming down by nearly 10 runs.
One of the signs of a great bowler is the number of times he can get through the defences of batsmen and hit the stumps, and in that aspect Zaheer has significantly improved his stats against right-handers. In 42 Tests in his first phase, he had dismissed right-hand batsmen 72 times, of which only six were bowled, a percentage of 8.33. Since his comeback, 12 out of 50 right-hand dismissals have been bowled, a percentage of 24. It is an indicator of his ability to get the better of batsmen with changes of pace, and swing and seam, and they all point towards his becoming a more complete bowler.
His performances against the top batsmen during this period are a mixed bag. He has had plenty of success against Andrew Strauss, Kumar Sangakkara and Ian Bell, who has been dismissed by him five times in 34 balls, but his record isn't as good against Michael Hussey, Ashwell Prince, Simon Katich and Kevin Pietersen. Even among these batsmen, though, most will agree that the Zaheer Khan of today is a far more aggressive, penetrative and relentless fast bowler than the version of four years ago.