Kapil Dev: Stats analysis - India's first fast-bowling match-winner
.........Kapil's best phase as an ODI bowler coincided with two famous victories in world events for India.
During the period between May 1983 and March 1986, when India won the World Cup and the World Championship of Cricket, he averaged 31.25 with the bat and 20.39 with the ball, taking 69 wickets in 47 games. His performances remained impressive till the early 1990s, but in the last couple of years of his career his numbers fell away alarmingly: in 36 matches he averaged 13.50 with the bat and more than 37 with the ball. The only aspect that wasn't affected was his economy rate, which remained well below four runs per over.
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The aspect of his ODI bowling that stands out best is his economy rate. Admittedly, Kapil played in an era when ODI scores hadn't reached the astronomical heights they have today, but even among his contemporaries, his economy rate was among the best.
Of the 212 games in which he bowled at least five overs, 63 times he conceded fewer than three runs per over, which is 30% of those matches. Similarly, in another 32% his economy rate was between three and four. Only 34 times did he go at five or more per over.
A statistical analysis of Kapil Dev's career | Cricket | ESPN Cricinfo