The manner in which Guerin collapsed to the ground in the second quarter of her team's thrilling five-point loss to the Saints sparked fears that she had become the fourth Melbourne player to rupture her ACL this season.

With eight AFLW players in total already sidelined for lengthy spells after rupturing their ACLs this year, an epidemic of the serious knee injury has seemingly swept through the competition.

Fortunately for Guerin, initial indications are that she has dislocated her kneecap, which would be a less serious injury, but so distracted was McCarthy at the time of the injury that she took the unusual step of asking Melbourne captain Daisy Pearce if the game should be stopped while Guerin was grounded.

"To be honest, personally I was a little bit shaken from that seeing that happen because there's so many ACLs that happen in our game and it just didn't look great," a visibly upset McCarthy said post-game while choking back tears.

"You just feel for the player, regardless of what jersey they're wearing, that's a pretty tough injury to come back from.

"I was actually a little bit disappointed we didn't stop the game because she was kind of in the middle of it.

"I was next to Daisy actually and I was like, 'Do we need to stop?' And she said you've just got to keep going. It's not nice to see anyone go down like that."

Pearce appreciated McCarthy's concern but insisted Guerin's injury wasn't a reason for Melbourne's loss.

"I don't think it affected our night tonight, in the nicest possible way," Pearce laughed. "I hope that doesn't sound too brutal."

Forward Caitlin Greiser was outstanding for St Kilda, having a hand in each one of her team's three goals, scoring two, including a match-winning bomb from 50 metres out, and setting up the other.

And McCarthy believes Greiser has only scratched the surface of her enormous potential.

"She's growing in confidence every week, I think look out [opposition] teams if she gets even more confident in her ability," McCarthy said.

"She's going to be something else and she's still got heaps to learn but that's the really exciting part about it because you saw what she could do tonight and in my opinion I think she can improve on that 10-fold."

Australian Associated Press