McCulloch was sent off for an elbow into the face of Osman Sow in the Light Blues 2-1 victory over Hearts.
The 36-year-old faces a spell on the sidelines with a two-game ban but McCall warned it could be more.
“Lee made a poor decision. I understand why he did it but it was a blatant red card. He led with his elbow and it was wrong – but he knows he was wrong.
“He has got to take his punishment and move on now. He has got a two-game ban – whether he gets back in the team thereafter we will see.
“Since I’ve been at the club he has done fine. He’s been good in the dressing room and his performances have been good.
“If whoever comes in over the next two games does really well, then he might not get back in.
“He’s not undroppable no, but at this moment in time with the games we have played he has done nothing to merit being dropped.”