It's the world-class, Roger Federer-like slice backhand that holds the key to her Australian Open title chances, but Ash Barty shouldn't expect many coming her way in Thursday night's semi-final.
That's the belief of Australian coach and master tactician Craig O'Shannessy, who has helped orchestrate Madison Keys' updated game style to crush Barty's Open dreams at Melbourne Park.
A one-time close ally of Novak Djokovic who sat in the world No.1's courtside box for four of the Serb's 20 grand slam crowns, O'Shannessy was head-hunted last year by Keys' IMG management to navigate the US star's way out of an alarming form slump.
And while working with Keys in Florida, O'Shannessy was not only instrumental in reviving the former US Open finalist's career, he also armed the one-time teenage prodigy with the clever strategy to bring down Barty.
"The first thing you need to understand is what Barty's weapons are and it's her slice backhand - in spades," O'Shannessy told AAP on Wednesday.
"No question, what sets Barty apart is her wicked slice backhand. So if Madison Keys overplays the Barty backhand, she'll be on the next flight home.
"If Madison Keys does win this match, it'll primarily be because she turned it into a forehand-to-forehand battle."
Hence why the potential Barty pooper is urging Keys to pepper the top seed's forehand wing, just like fellow American Alison Riske did so successfully at Wimbledon in 2019.
That loss to Riske was the reigning Wimbledon champion's last defeat at the All England Club when O'Shannessy was also charged with devising Riske's winning game plan.
"When I worked with Alison Riske at Wimbledon, the goal was to not let Ash Barty hit slice backhands at all," he said.
"In tennis, most rallies between two right-handed players go through the ad (advantage) court.
"If you go deuce court then you're playing strength versus strength and Ash can potentially get wild with forehands.
"She has a tendency to mis-hit when pressured deep and wide to the forehand."
Barty's coach, though, is unfazed about the prospect of Keys trying to starve his superstar charge of backhands.
Trusted mentor Craig Tyzzer has no doubt Barty has sufficient other strengths in her artillery to combat Keys' aggressive tactics.
"Ash has other attributes," Tyzzer said.
"Her forehand is actually a weapon.
"Her slice will set her up a lot for her forehand. Her serve sets her up a lot for her shots as well. It's all of those elements for me.
"There are a lot of those girls who hit big out there. It's being able to handle that pace but do something with your shorts as well."
