The preferred strategy for teams winning the toss in ODI matches that are expected to be significantly impacted by weather had been to bowl first and chase the D/L score. This is because the D/L method has more often than not, at least in theory, favoured the team batting second. Captains winning the toss during the on-going Tri-Nations event in the West Indies too opted for this strategy, but lost by significant margins under the D/L method.
As described by Wikipedia “The Duckworth–Lewis method is an attempt to set a statistically fair target for the second team’s innings, based on the score achieved by the first team, taking their wickets lost and overs played into account”. According to D/L logic, the team batting first is given the benefit of not knowing beforehand that their innings would be cut short due to bad weather. As to how much of a benefit the team batting first gets is determined based on how many wickets they had remaining and overs left to bat. Higher the number of wickets remaining and overs left to play for the team batting first when their innings was cut short, greater the required run rate is for the team batting second. Two recent examples from the Tri-Nation event in the West Indies help illustrate this point. West Indies only had to score 12 extra runs after Sri Lanka scored 219 in 41 overs, but lost 8 wickets. However, in the next match, Sri Lanka were asked to score 178 in 26 overs after India only managed 119 in the 29 overs they batted, but lost only 3 wickets. Sri Lanka had to score at a much higher run rate because India had 7 wickets remaining and 21 overs left to bat, when their innings was cut short.
While the present D/L method has been the best alternative to finding a statistically fair revised target for weather impacted matches, the use of two new balls in ODI matches make the current D/L method calculation of the revised target unfair to the team batting second. The current D/L calculations or projected scores have been formulated based on the study of historical scores from ODI matches played when there was only ONE new ball used, at least during the first 35 overs. However, with two new balls at the beginning of an innings even in shortened matches, teams batting second find it much harder to keep up with the required run rate as their batsman are exposed to TWO new balls during most of the allocated overs.
The team batting second in a D/L method applied ODI match using two new balls does not get the luxury of seeing off the pair of new balls. They are forced to take far greater risks to maintain the same run rate that teams batting second facing only ONE NEW BALL was asked to chase, when the present D/L method calculations were developed. In addition, the team batting second is often batting on a surface that had been exposed to rain and also been covered for a significant amount of time prior to resumption of play. As a result, the team batting second is challenged by two new balls on a lively surface and is forced to reach a challenging score in quick enough time that isn’t even long enough to take the shine off the new balls or dry the surface. The challenge is further compounded by the fact that the team batting second is often challenged to reach the D/L par score by the 20th over of their innings, which forces their batsman to take risks while the balls are still new. The two matches mentioned previously are good examples that illustrate this point. In both of those matches, teams batting second were effectively out of the match within the first 20 overs of their chase after losing at least four early wickets in pursuit of quick runs off of two new balls on difficult wickets.
Unless D/L method is adjusted to account for two new balls at the beginning of an ODI innings, or the ICC modifies the “two new ball” rule for shortened ODI matches, we might start seeing a shift in the preferred strategy of captains winning the toss in ODI matches where the D/L is expected to come in to play.