Tony Popovic's team will be without their talisman when Josep Gombau brings his Reds to Parramatta on Friday, potentially opening the door for an upset away win
Hersi was forced off at half-time of last weekend's 2-0 derby win over Sydney FC after he was stomped on in a tackle, with the pacy winger getting around in a moon-boot ever since.
Wanderers boss Tony Popovic revealed on Friday the Dutchman had been cleared of any major damage, with scans confirming only severe bone bruising.
But the problem hasn't cleared itself up in time for the visit of the Reds, meaning the Wanderers will have to make-do without the man who has been a key figure in their success.
The Wanderers are unbeaten in their last 20 matches Hersi has played, going all the way back to round seven of last season.
"He's improved a lot and it's just precautionary at the moment with the boot on but he won't play," Popovic told reporters on Thursday.
"The main thing is there's no serious damage. It's quite severe bone bruising and it hasn't quite settled enough.
"We want to do the best by the player. We're happy with how he's progressing but he won't be available tomorrow (night).
"But there's no serious damage which is most important thing."
Brendon Santalab replaced Hersi on the right against the Sky Blues and is an option against the Reds, along with the likes of Shannon Cole, Labinot Haliti and Tahj Minniecon.
Popovic said he would wait until after Thursday's final training session before deciding which way he would go with the make-up of his side.
"We've got a few options there, a few boys that have put their hand up for that role," the Wanderers boss said.
"So we'll have a final look today and make a decision."
Midfield lynchpin Aaron Mooy, who missed the derby due to concussion, has been passed fit and will play some part at Pirtek Stadium.
But Socceroos defender Matthew Spiranovic may be forced to wait another week before making his first appearance for the club.
"He's close," Popovic said of Spiranovic.
"He's like the other players, they all feel they are ready to go but I'd like to see him get some more training in for another week or two to see him at his best.
"That's not to say he couldn't play now but we'll wait and see."