Sporting greatness is often revealed in decisive moments. When drama and talent intersect. An athlete facing high stakes rising to the occasion when it matters most.

On Saturday, over the course of six hours in suburban Sydney, three such moments were delivered across two semi-finals of this year's WBBL.

First was the catch

Brisbane's Haidee Birkett showing nerves of steel to take a high ball on the boundary to deliver a last-ball victory over the Sydney Thunder.

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Then the run out

With three runs needed off the final delivery to win, Melbourne Renegades' Sophie Molineux heaved one towards the boundary for what looked for certain to be the winning score. Not so.

Erin Burns' dramatic dive prevented it reaching the rope, allowing Sarah Aley to return the ball to wicketkeeper Alyssa Healy, who showed lightning reflexes to produce a direct hit at the none-striker's end as the Renegades scrambled in vain for the match-winning run, instead forcing a Super Over.



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And, finally, the shot

Ellyse Perry stepped up in the sudden-death moment to launch a huge effort over the rope for a maximum that booked the Sixers' place in this weekend's final.

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As far as this Australian cricketing summer goes, these three moments may stand as the most memorable. But — without minimising the efforts of Birkett and Burns — it's the last of these three that tells the biggest story of the WBBL season to date, and provides the key to the showdown for the title on Saturday when the Sixers and Heat meet at Drummoyne Oval.

Perry just gets better and better

Over the course of her career in professional sport, Perry, for all her match-winning exploits, early on arguably was foremost a player whose game was built on defensive qualities (her pace bowling aside).

From her days as a defender for the Matildas, Canberra United and Sydney United, to her anchoring batting performances for the Southern Stars, Perry's brilliance was best described as being ruthlessly measured rather than explosive.

Ellyse Perry has 744 runs to her name in this year's WBBL is the competition's stand out performer with the bat. ( AAP: Brendan Thorne )

There were signs this approach might have been changing during her performances in England's Women's Cricket Super League, where she racked up the runs at a strike rate of over 120 across two seasons, but at WBBL level her strike rate hovered below a run a ball.

This year, Perry's rate of scoring has risen to 123.17 runs per 100 balls, good for 14th across the entire competition (minimum of 100 balls faced).

While she has only faced 44 more balls (so far) than her WBBL3 season, she has managed to score 192 more runs in that time. Almost every level of her attacking game has improved year on year, including her ability to hit the long ball, as she did to such devastating effect on Saturday.

Few players, male or female, have been able to score as many runs as her 744 this season across any domestic T20 competition.

In fact, Perry's current season would place her as having the third most runs of any single player's performance across any elite T20 competition, behind Virat Kohli and David Warner's 2016 IPL seasons.

Just how special is Perry's season?

To try to dig a bit further, and to adjust for changing times and season lengths, we've created a series of measures using a technique called z-scores that finds how "exceptional" a season is compared with the rest of the competition that they have faced.

This technique adjusts for the overall trends and conditions present in any given year.

Two primary factors to batting performance in T20 cricket are considered: runs per innings and strike rate. The two scores are then averaged to find the overall result — how much better than the average player they have performed.

Across the four WBBL seasons, Perry stands in second at this stage, just a shade behind Meg Lanning's stellar WBBL1, where she led the competition in batting average and runs per innings and was eighth for strike rate.

With a good performance on Saturday, Perry may leapfrog Lanning into the top spot.

When adding the BBL into the mix, the true dominance of Lanning and Perry firmly fall into focus.

Only exceptional half seasons by Usman Khawaja and Chris Lynn top those two out, with D'Arcy Short's full campaign last year also firmly in that grouping.

So how will the Heat try to stop Perry and co?

Despite the natural focus on Perry, the bad news for the heat is that she has a number of accomplished teammates that can more than hold their own with the bat. Names like Healy, Ashleigh Gardiner, Burns and Dane van Niekirk would be centrepieces in any team in the competition.

But the Heat are blessed with one of the more diverse attacks in the competition, with slow bowlers and quick, both able to restrict the scoring and take wickets.

Brisbane will be faced with a decision early on — to attempt to slow the scoring of Perry with bowlers like Birkett or Sammy Jo-Johnson, or attempt to take wickets with options like Delissa Kimmince or Jemma Barsby.

While a slow bowler, Grace Harris may be a compromise between the two camps, as the third most economical regular bowler in the league and with the ability to take key wickets.

If the Heat can manage to limit Perry to being merely the elite player of previous WBBL seasons, instead of her current otherworldly form, they still will have a challenge in chasing down any total considering the depth of the Sixers bowling attack.

The Heat have a wealth of bowling talent in their ranks and enter this weekend's final with belief. ( AAP: David Neilson )

South African Marizane Kapp tops the WBBL for economy rate this season, and has proven herself over each level of the game across the world.

Beyond Kapp, the Sixers have four of the 12 most economical bowlers this season, providing their ability to strangle almost any opponent.

Perry isn't among those four (given she often bowls in high-leverage situations) but her role with the ball, and the wicket threat she carries, can't also be understated.

In short, even if the Heat can put the shackles on Perry — and it is a big if — they'll have to then worry about the quality elsewhere in the line-up.