How McCullum's effort saved a six

Brendon McCullum's athletic boundary-line save in the KFC Big Bash has once again sparked confusion among even the most savvy of cricket fans.

While he couldn't complete the dismissal, McCullum's terrific effort on the long-on rope denied the Sydney Sixers a crucial boundary in the final overs of their first innings at the SCG on Sunday evening.

After initially taking the catch off a James Vince skied drive, McCullum threw the ball up as he begun to lose his balance, but only managed to lob it up to himself.

At this point the former New Zealand captain, whose entire body was now on the other side of the boundary rope, briefly jumped up off the ground to parry the ball back into the field of play. No part of his body was touching the ground when he made contact with the ball.

Under the old rules which many cricket fans grew up with and knew by heart, the attempted save would have been a six.

However an October 2013 update to the Laws of Cricket means McCullum's act was correctly adjudicated as a save and resulted in the Sixers and Vince being awarded only the two runs they ran.

The major points of the rule, according to the MCC, are as follows:

- The key part, in terms of positioning, is the fielder’s first contact with the ball during the passage of play.

- The fielder's first contact with the ball must be made inside the boundary.  If he is airborne when making this first contact, he must have taken off from within the boundary.

- The ball then can be fielded or caught, as long as the fielder is never in contact with both the ball and the ground outside the boundary at the same time.

- So, on a second or third contact with the ball, the fielder can jump up from beyond the boundary and parry it back inside. He can do this as many times as he wants, as long as he is never in contact with the ground beyond the boundary while he is touching the ball.

The rule has caused controversy in the past.

Sam Billings, in England's T20 match against the Prime Minister's XI last summer, caught James Faulkner in the deep at Manuka Oval and, as momentum was about to take him over the rope, he tossed the ball into the air. After running over the boundary, he then turned and jumped from outside the rope, caught the ball while still in the air and then landed back in the field of play.

While many on social media were quick to cry foul, Billings' effort was rightly adjudged out.

Perhaps the famous incident was one involving Glenn Maxwell, who took a classic catch at Headingley in an ODI against England back in September 2015 by utilising his knowledge of the rule.

Maxwell's intimate understanding of the Law had come about eight months earlier, when he took to Twitter to criticise a catch from then Sydney Thunder player Josh Lalor in the KFC Big Bash after the player jumped from beyond the boundary rope back into the field of play.

Chastened to discover the catch was in fact legal, Maxwell showed he had not forgotten the lesson later that year, as he completed a similar if altogether more acrobatic and stunning catch that traversed the boundary rope on the international stage.

When it came to Billings' catch, it was clear that the rule remained a vagary in the game, with plenty on questioning the legality.

Others suggested the Law should be changed, however given the update came about in order to provide the best outfield catchers with a greater opportunity to display their wares on the rope, it appears a return to the original rule is unlikely.