REIGNING premier Adelaide has suffered a horrible blow at the start of pre-season, with co-captain Chelsea Randall tearing the ACL in her right knee.

Randall was changing direction in a drill at the first pre-season session on Monday night when her knee buckled and she has been ruled out for the season. 

The Crows could now have five players missing 2020 with knee injuries including Randall, superstar Erin Phillips, Chloe Scheer, Rhiannon Metcalfe and Hannah Button (nee Martin).

Randall, 28, is the best intercept defender in the competition; a three-time Virgin Australia AFLW All-Australian (named captain in 2018) and three-time AFLPA most courageous player. 

She also won Adelaide's best and fairest in 2018 and is the general of the team's well-disciplined backline. 

It leaves the Crows with a leadership vacuum, as fellow co-captain Phillips (pictured below with Randall) is still no certainty to play in 2020, having torn her left ACL during the 2019 premiership win at the end of March. 

Star youngster Scheer also tore her right ACL in the Grand Final, while ruck Metcalfe tore her left ACL in a practice match at the start of 2019. 

The Crows are hopeful they will regain the trio for 2020, but it is still too early to tell if any will be fit.

FULL FIXTURE Every round, every game

Button was ruled out for the season in early July when she tore her right ACL playing for NT Thunder in the VFLW. 

As the injury occurred before October 11's cut-off for inactive players, the Crows received an extra pick in the NAB AFLW Draft as cover. 

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Phillips, Metcalfe, Scheer and Randall are not on the inactive list, meaning Adelaide currently has just 26 fit players at this early stage of pre-season. 

A rarely used injury replacement rule, which kicks in when teams have fewer than 24 fit players available, may be an option for the Crows when February's round one approaches.