Under the new system, teams have to begin the final over of the innings by the 85th minute since the start of the innings. As Sri Lanka had not done so, captain Dasun Shanaka was asked to move one of the five fielders he would have stationed on the boundary, into the circle. That over, delivered by debutant Nuwan Thushara, went for 16, after Matthew Wade struck a six and a four on the leg side.
On the eve of the match, Australia's interim coach Andrew McDonald had expressed support for the rule change.
"There is a criticism of T20 cricket that sometimes the games drag out, so if that penalty is there, you let a bowler know that he's bowling with four men out versus five men out, it's a pretty clear choice which one he wants," he had said. "It's very difficult to bowl with four men out. I think you'll see that rule potentially shifting games and I love to see it. The in-game penalty, for me, is the only way forward to deter teams from slowing the game down."
The new rule has already come into effect once in women's T20Is, with Australia penalised for their slow over rate during the first T20I of the Women's Ashes recently, leaving Megan Schutt with only four fielders outside the circle when she began the final over of England's innings.
Previous penalties for slow over rates had included suspending captains and fining teams portions of their match fees. Both in the ODI Super League and the World Test Championship, teams can also lose league points for slow over rates.