A fortnight after inking her first full-time contract, the Horsley teenager was substituted into the game at halftime in Saturday night's clash with the Western Sydney Wanderers at CommBank Stadium.

It was an opportunity that the 18-year-old will never forget. However, the biggest moment of her young career was still to come.

After Figtree's Mackenzie Hawkesby scored Sydney FC's first goal midway through the second stanza, Tallon-Henniker then etched her name into the club's record books in stoppage time.

A beautiful through-ball from Cortnee Vine put Tallon-Henniker into a paddock of space, with the speedster running the ball into the box before stepping onto her right foot and beating the Wanderers goalkeeper.

The 93^rd goal ensured that the sky blues had claimed bragging rights over their biggest rivals.

"I've obviously been dreaming about how my debut would go for a while, and I was thinking that I'd maybe get five or 10 minutes at the end of the game. So to get 45 minutes in the Sydney derby - and score a goal on top of that - it was incredible," Tallon-Henniker told the Mercury.

"(Head coach) Ante (Juric) told me before I went on to enjoy the moment, have a look around at the crowd and soak it all up. So I went out, I was looking around and thinking 'wow, I can't believe I'm actually doing this'.

"I was very nervous (running towards goals). I kept thinking 'please don't mess this up, please go in'. But I just went back to what I've been working on at training. Ante always told me to hit the corners, so I did, and it went in.

"It doesn't get any better than playing on Western Sydney's turf, and to get a win against them."

Saturday's debut continues Tallon-Henniker's incredible rise in football.

A rugby league and union convert, the teen was elevated to Sydney FC's squad as a train-on player ahead of the 2023/24 season. She was also called up to represent their club at the AFC Women's Club Championship in Uzbekistan last November.

Tallon-Henniker continued to impress the coaching staff throughout the sky blues' campaign, earning herself a full-time contract in February as an injury replacement for Fiona Worts as she recovers from a serious knee issue.

Saturday marked Sydney FC's eighth win of the season, with the sky blues sitting in third spot on the table.

"It would now be great to hopefully get some consistent minutes. To cement my spot off the bench, or even the starting side, is my goal for the rest of the season," the speedy winger said.

"The girls all have my back, and they're super proud of me for backing myself. So hopefully I have their support - and the coaching staff's - and they continue to play me.

"We have a big clash this weekend with Western United, so we want to win that one. Hopefully we can then win the rest of our games and come top of the ladder.

"That's our main goal to start with. We'll then go into the finals series, and get a win in the grand final."