Sri Lanka secured their place in the final of the 2023 Asia Cup after a thrilling last-ball win over Pakistan on Thursday.
Kusal Mendis' 91 and an unbeaten 49 by Charith Asalanka helped Sri Lanka edge out Pakistan by two wickets.
Chasing a DLS revised target of 252 in the 42-overs-a-side contest in Colombo, Sri Lanka needed eight from the final over and achieved the target with Asalanka's winning hit on the last ball at 1.07am local time.
An explanation of the DLS method and its reason for being used is below.
What is the DLS method?
The DLS method (Duckworth-Lewis-Stern) is used to help decide the winning side in an unavoidable situation for the team batting second in limited-overs cricket.
It is a mathematical formulation designed to calculate the target score for the chasing team during a match interrupted by weather or other factors.
Who invented the Duckworth Lewis method?
British statisticians Frank Duckworth and Tony Lewis devised the formula and for a long time it was simply referred to as the DL method. Professor Steven Stern became the custodian of the method after the retirement of Duckworth and Lewis. In November 2014, the Duckworth–Lewis method was renamed the Duckworth-Lewis-Stern method, or DLS method.
When was it first used?
The Duckworth Lewis Method was first used in a match played between Zimbabwe against England in 1996-97, which Zimbabwe won by seven runs. It was formally approved by the International Cricket Council in 1999.
Why is it used?
When overs are lost, setting an adjusted target for the team batting second is not as simple as reducing the run target proportionally to the loss in overs, because a team with 10 wickets in hand and 25 overs to bat can play more aggressively than if they had 10 wickets and a full 50 overs, for example, and can consequently achieve a higher run rate.
The DLS method is an attempt to set a statistically fair target for the second team's innings, which is the same difficulty as the original target. The basic principle is that each team in a limited-overs match has two resources available with which to score runs (overs to play and wickets remaining), and the target is adjusted proportionally to the change in the combination of these two resources.
Difference between par score and target score
Par score is the total that a chasing team should have reached – when they are ‘X’ wickets down – at the time of interruption while the target score is the revised score that a team is required to get after an interruption.
The target score is one fixed number, while the par score changes according to the number of wickets lost. The par scores are calculated before an interruption, while targets are calculated after an interruption.
How is DLS calculated?
Essentially the DLS method factors in each team's 'resources'. Each team starts the match with two 'resources' to use to score as many runs as possible: the number of overs they have to receive; and the number of wickets they have in hand. At any point in any innings, a team's ability to score more runs depends on the combination of these two resources they have left.
The method converts all possible combinations of overs and wickets left into a combined resources remaining percentage figure (with 50 overs and 10 wickets = 100 per cent), and these are all stored in a published table or computer. The target score for the team batting second ('Team 2') can be adjusted up or down from the total the team batting first ('Team 1') achieved using these resource percentages, to reflect the loss of resources to one or both teams when a match is shortened one or more times.
To calculate a target, the formula may simply be expressed as:
Team 2's par score = Team 1's score x Team 2's resources/Team 1's resources.
Watch this ICC explainer: