The Australia international tore the PCL in his right knee in the 4-3 win over Real Salt Lake last weekend which forced him out of the NMLS All-Star game last week and Saturday's 3-2 triumph at Sporting Kansas City.
Petke suggests the initial time frame of four weeks out remains the guide for Cahill.
"(He) continues to do very well. He will not be involved in the Columbus game this weekend, and anything after that depends on how he continues to rehab and continues to respond to the treatment he's getting," said Petke.
"I'd love to give you best-case and worst-case scenario, but I really can't do that at the moment. He's doing well; he's improving."