Bowling variations
Why the slower ball belongs at the death
Sam Curran has made a trademark of the moon ball, a looping delivery from a left-arm seamer whose usual pace sits near 130 kph. In speed readings from men’s T20s and ODIs since 2011, his moon balls average about 82 kph, or 51 mph. In the opening match of the 2025 Hundred he took 3 for 18, and two of those wickets came with the moon ball itself, Richard Gleeson bowled by one clocked at 75.6 kph. Curran is back in England’s white-ball sides in 2026, and his moon ball is an unusually slow version of a delivery most seamers now bowl: the slower ball.
Seamers bowl it at every stage of an innings, the powerplay included, and that habit deserves a harder look. In the T20 powerplay a seamer’s slower ball concedes 13 runs per 100 balls more than his own stock ball, about three-quarters of a run an over.
Taken across both formats, the figures make the slower ball a weapon for the death overs. It shows a profit when batters are at their most aggressive, at the end of an innings, and at every other stage it costs runs, even against batters who swing as hard earlier on as they do at the death. Bowlers do not yet appear to have learnt this. They already keep more of their slower balls for the end, but they still bowl too many in the overs before it, where each one costs runs.
How much slower is a slower ball?
For our purposes, a slower ball is one bowled at least 10% under the bowler’s usual pace in that innings, whatever grip or method the bowler uses to take the pace off it.
Curran’s moon ball sits far beyond that line, in a smaller family: the very slow ball, 30 kph or more under a bowler’s usual pace, which from a seamer typically means about 100 kph. Curran bowls balls that slow more often than all but five of 63 seamers with a long T20 record, and the bowlers who bowl them most are slower-ball specialists. Taken across every seamer who bowls it, the very slow ball, like the ordinary slower ball, fares very differently depending on when in the innings it arrives.
Why do slower balls go for runs in the powerplay?
Early in a T20 innings the slower ball fails at what it is meant to do: beat the bat. In the powerplay it draws 4 fewer false shots per 100 balls than the stock ball, and batters hit it to the boundary more often as well.
Seamers already bowl it sparingly at this stage, with slower balls making up 6% of their balls in overs 1 to 6, the smallest share of any stage of a T20 innings. Even that share is too high, because each of those balls concedes more than a seamer’s stock ball does in the same overs.
Do slower balls work in the middle overs?
Again, no. In T20 middle overs a seamer’s slower ball concedes 9 runs per 100 balls more than his stock ball.
It fares no better in the middle overs of an ODI, where it draws 2 more false shots per 100 balls than the stock ball and still costs runs.
When should you bowl a slower ball?
At the death, in overs 16 to 20. The extra cost of a slower ball shrinks as a T20 innings goes on, and by the last five overs it no longer costs runs against the stock ball.
It gets there by beating the bat, drawing 5 more false shots per 100 balls than the stock ball without going for any more boundaries. Off the bat it still gives away slightly more than the stock ball, but its extra wickets make up the difference. For a bowler trying to close out an innings, that makes it an appealing proposition: a change of pace that costs him nothing.
In the death overs of an ODI it does better still, saving 10 runs per 100 balls against the stock ball. It pays more there for two reasons. Off the bat it gives away fewer runs than the stock ball, and each wicket it takes costs the batting side more at the end of an ODI than at the end of a T20.
Why does the slower ball work at the death?
It pays at the stage when batters are swinging the hardest. In the last three overs of a T20, batters take a big swing at nearly half of a seamer’s slower balls, about twice as often as at his stock ball, while in the powerplay the gap between the two is much smaller.
That link does not carry back into the earlier overs. Before the death, even against the batters who swing hard as often as batters do at the death, the slower ball still costs about 3 runs per 100 balls more than the stock ball, and against batters who swing less often it costs 5 to 11. So a bowler cannot rescue the middle-overs slower ball by saving it for the batter who is already on the charge.
Stock ballSlower ball
Do very slow balls like the moon ball work?
No, not even at the death. In T20 middle overs a very slow ball concedes 39 runs per 100 balls more than the bowler’s stock ball, more than two runs an over, which makes it the costliest ball a seamer bowls at that stage. The middle overs of an ODI are almost as unforgiving.
At the end of a T20 innings it gains twice as many extra wickets over the stock ball as the ordinary slower ball does, but batters score so much more freely off it that those wickets never cover the runs.
At the death, whether the batter is set changes what the ordinary slower ball is worth, but it does nothing for the very slow ball. Against a batter who has faced fewer than six balls, the ordinary slower ball saves 6 runs per 100 balls against the stock ball, while against one who has faced 15 or more it concedes 5. The very slow ball costs runs against new and set batters alike, so no situation at the death excuses it. For the ordinary change of pace late in an innings, the best moment is the first few balls to a new batter.
What is the best ball to bowl at the death?
The yorker, by a distance, and here traditional wisdom is right. Set against a bowler’s average ball at the end of a T20 innings, a yorker saves 71 runs per 100 balls, far more than any other ball he can bowl, while the slower ball sits close to that average.
In the death overs of an ODI the yorker again stands well clear of every other ball, with the slower ball the next best of the deliveries bowled often.
Traditional wisdom falls down on the effort ball, 6% or more above a seamer’s usual pace, which costs more runs than the stock ball in every phase of a T20, as much as 37 runs per 100 balls more in the powerplay. Nor does keeping the batter guessing pay in general: how much a seamer varies his pace from ball to ball or over to over makes no measurable difference to the runs he concedes or the false shots he draws.
How hard is it to bowl a yorker at the death?
Hard, because the target is only about 3 metres long: at the death a ball near the bowler’s usual pace saves runs only if it pitches within about 3 metres of the stumps. Overpitch it and the ball arrives on the full as a full toss; drop it a touch short and it lands as a half-volley.
Few seamers land it often: only about 7% of their death balls near their usual pace arrive as yorkers, fewer than arrive as full tosses. The sums still favour trying, because a bowler aiming at the yorker beats a good-length ball by landing about one attempt in six, even if his misses cost what full tosses and half-volleys usually cost.
It also keeps its value when a batter has seen it before. Once he has faced one yorker from the bowler, a later one still saves about three-quarters as many runs as the first, far more than any other ball, and bowlers who bowl the most yorkers get as much from each one as those who bowl the fewest.
Are bowlers using the slower ball in the right overs?
Not yet, though any criticism needs tempering, because seamers already lean towards the death. In T20s their share of slower balls climbs through the innings to 18% in overs 16 to 20, and ODIs follow the same climb towards the last overs, so the broad shape is right.
The trouble lies in the overs just before the death: in T20 overs 11 to 15 about one ball in seven is still a slower ball, the highest share of any stage before the death, and each one concedes 8 runs per 100 balls more than a stock ball would.
Some bowlers have the balance the wrong way round altogether: 17 of 58 seamers with long T20 records bowl a larger share of slower balls in the middle overs than at the death. For them the delivery is spent most freely where it costs runs, and used more sparingly where it pays.
So when is a slower ball worth bowling?
At the death, in both T20s and ODIs. Before that the stock ball is the better delivery in either format, so what a slower ball is worth comes down to the discipline a seamer shows in choosing the overs he bowls it in.
Every slower ball bowled before the death costs runs against the stock ball, and T20 overs 11 to 15 are where they cost seamers the most runs in all. Each slower ball there costs less than one in the powerplay, but far more of them are bowled, so that is where bowlers and their coaches should start cutting.
The very slow ball is the most extravagant use of the slower ball there is. It is the dearest ball a seamer bowls in the middle overs. At the end of a T20 innings, where it takes wickets fastest, those wickets still never cover what it gives away off the bat. The moon ball makes a fine spectacle, but across every seamer who bowls one it pays its way at no stage of an innings. The rational choice is to leave the very slow ball out altogether, and keep the ordinary slower ball for the last overs.