For all the talk about Milos Ninkovic's defection to Western Sydney, the decision to let Calem Nieuwenhof switch to their rivals could be the call Sydney FC regrets the most.
Nieuwenhof is flying this season and his form in A-League Men has already led to him being linked with a move to Ange Postecoglou's Celtic.
A graduate of the Sky Blues' academy, Nieuwenhof remembers watching derbies from Sydney's active supporter bay, The Cove.
After first breaking into the first XI in 2020, injuries hindered his progress and Sydney opted against offering him a new deal at the end of last season.
Wanderers boss Marko Rudan was straight on the phone to the 21-year-old, who is now relishing being on the other side of the city's dividing line.
"It was a confusing time because I had struggled with injuries over the last couple of seasons," the midfielder told AAP ahead of Saturday's derby.
"I was in limbo and then the opportunity to join the Wanderers came along and I've not looked back.
"It all came a bit out of the blue and I feel like I've developed a lot over the past few months.
"I was a Sydney FC fan growing up but now I'm at the Wanderers, I'm a Wanderers supporter."
Sydney had concerns over the midfielder's body but the Wanderers appear to have got the youngster firing on all cylinders.
Nieuwenhof has played every game this season for Rudan and has only been substituted once.
While his manager has dismissed the Celtic link as pub talk, it wouldn't be a surprise to see more serious conversations develop if his upward trajectory continues.
"That (a mooted move to Celtic) was pretty crazy to hear," Nieuwenhof said.
"It surprised me as much as anyone.
"It was a rumour, but it was a rumour that tells me I'm doing things right, and that's encouraging.
"I want to keep building throughout this season and keep putting in good performances."
That starts with this weekend's derby.
The Wanderers won the first encounter earlier this season and have made a habit of picking up points when the pressure is on.
"One of the best things about Marko is that he gets us motivated," Nieuwenhof added.
"Before the last derby his speech was really inspirational and we reacted positively to it.
"I think this weekend will be no different, everyone is going to be really fired up."
