Hooker didn’t play in the Bombers’ opening JLT Community Series game but was scheduled to face Geelong this weekend, although he’ll now be forced to watch on from the sidelines.
Essendon’s physical performance manager Justin Crow said Hooker would be looking at a four to six week recovery period given the nature of the injury.
“Cale was doing the last training session before he was due to return for JLT (game) two,” Crow told the club’s website on Tuesday.
“Unfortunately for Cale, he’s picked up a soleus injury – a calf strain – that will cost him six weeks.
“Cale had been doing everything right, he’s a professional.
“It’s disappointing news for us and him, but we’ll have to get back to rehab and keep building him up towards an early-season return.”
Crow also touched on Dylan Shiel’s quad injury, although the new Don is expected to face Geelong on Thursday after pulling up well.