Heskey underwent scans on his left knee on Thursday which revealed a grade two strain of his medial ligament, with the diagnosis a blow to the Jets, after coach Gary van Egmond had suggested the marquee centre-forward could be back in less than a month.
Former England international Heskey, who limped off following a tackle by Victory centre-back Nick Ansell, is slated to return for the round four game at home to the Central Coast Mariners on November 2.
The Jets won the warm-up match against Victory 1-0 courtesy of a second-half penalty from James Virgili, but Van Egmond was not pleased with his growing injury list.
"That's not what you want to get out of these games, these games are about getting match fitness and starting to work on the way in which you play," van Egmond said.
"It's not about flying in and getting people injured."
In what was a fiery match for a pre-season encounter, several full-blooded challenges were made, with a tackle from Connor Chapman on Mitch Nichols drawing an angry reaction from the Victory staff.
Van Egmond believes such incidents are down to the excitement the players feel when stepping onto the field against top-level opponents following a lengthy break.
"The boys don't play for quite some while and the pre-season is so long so they really look forward to obviously getting back on the park and playing A-League opposition," he said.
However, he did concede that some of this enthusiasm may be down to the role the coaches' play in the build-up to the new campaign.
"From us coaches we also want that to be very, very intensive in regards to what they are doing and making sure they're ready for the first game so sometimes we might ask for a little bit too much."
Aside from the intensity of the match, which van Egmond believes Victory dominated with the ball, the coach was pleased with his side's efforts when not in possession.
"We controlled the game without the ball, from the point of view that we didn't look to press high, we kept compact," he said.
"Once we made a few adjustments for the second half in regards to the pressing, we were reasonably quite comfortable in that second half."
Van Egmond is expecting a number of players to return to full fitness before the start of the A-League, but has praised the players who are performing well in pre-season.
"A couple of boys probably haven't been in the minds of everyone in regards to starting and doing well," he said.
"People like Mitchell Oxborrow for example... there's a few boys who are really starting to stand up."
The Jets kick off their 2013-14 season away to Sydney FC on October 11.
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