The 30-year-old passed concussion protocols after his head hit the turf early in the 3-2 loss to City at AAMI Park on Tuesday but was substituted shortly afterwards.

Ongoing symptoms have forced the Sky Blues to make the decision not to make Brattan available for the clash with the Bulls at Netstrata Jubilee Stadium.

"You can't take any risks with this situation," Sky Blues' coach Steve Corica said.

"As much as I know Luke wants to play, we will have to do without him this weekend."

It's not the first time Brattan has suffered a serious head knock on the field.

An FFA Cup match in 2018 was halted for 30 minutes after the then-Melbourne City player collided with Stefan Mauk in a game against Brisbane at Redcliffe.

Despite fears of a serious spinal injury, Brattan was subsequently cleared of any injury at hospital.

Brattan was also involved in an incident in 2017 when he played out a match against Central Coast despite reports a match-day doctor had advised he not return following a second-half head knock.

That incident sparked a debate about concussion protocols in the A-League but then City coach John van 't Schip played down any talk Brattan had overruled medical advice.

Youngster Calem Nieuwenhof, who replaced Brattan on Tuesday, appears the most likely candidate to move into the Sky Blues' starting XI for the clash with third-placed Macarthur.

Brattan is expected to be fit for Sydney's trip to Queensland to play Brisbane on March 6.

Australian Associated Press