Melbourne Victory's A-League Women title defence has been dealt a brutal setback with captain Kayla Morrison confirming she suffered a season-ending ACL injury in their season opener against Adelaide United.

Victory's thumping 5-1 win was soured after just 33 minutes when Morrison went down clutching her knee, in seemingly innocuous circumstances, and was forced from the field.

After having scans the 25-year-old, who replaced Angela Beard as captain ahead of the current campaign, confirmed the severity of her injury on Tuesday.

"Unfortunately, in our game on the weekend I did my ACL," Morrison said on Instagram.

"However, this just happens to be a part of the game we sign up for with sport.

"Maybe I needed to experience this low to fully and truly appreciate the highs that come along in careers.

"I'm ready to start the journey back and couldn't be happier or luckier to have the people I do behind me."

Morrison, who will have surgery this week, had also scored a goal before suffering the injury.

The American is one of the best central defenders in the league, earning a spot in the 2020-21 PFA team of the season and leaves a massive hole in Victory's backline.

"Our worst fears were answered today with the news of Kayla's injury and she'll be a massive loss to the squad for the remainder of the season," coach Jeff Hopkins said.

"Everyone at the club - from the men's and women's teams to the administration staff - have showed their support for Kayla and we will do everything we can to help Kayla return to the pitch.

"Lia Privitelli will take the captain's armband on the pitch for the rest of the season but Kayla will still be instrumental to our title defence with her leadership off the pitch."

Matildas defender Courtney Nevin could shift into a central role after playing left-back first-up, while Emma Robers deputised for Morrison on Sunday.

Victory will hope Nevin recovers from hamstring soreness and faces Melbourne City this Sunday, while star recruit Lynn Williams (international clearance) should play and striker Melina Ayres (hamstring tightness) will push to return.