Heskey suffered a corked calf in last Wednesday's 2-1 win over Wellington Phoenix and was rested by Jets coach Gary van Egmond, along with fellow English veteran Michael Bridges, from Sunday's 5-0 loss to Melbourne Victory.
"Unfortunately, Emile has suffered a fatigue injury and won't be playing in Friday's game," Van Egmond confirmed in an online fan chat on the Jets website on Tuesday morning.
"Scans today (Tuesday) will reveal more."
Jets physiotherapist Robert Dingle explained just how the club's busy schedule - of four games in 14 days - played a role in Heskey's injury trouble.
"Soft tissue injuries, like Emile's strained calf, are a bi-product of fatigue," Dingle wrote on the Jets website.
"Emile got a cork in his calf in the Wellington game, add to that the travel, which have both contributed to the injury he sustained at a light training session on Monday.
"We obviously made the decision to rest him on the weekend to avoid injury, so it is particularly disappointing to lose Emile now."