Windhager was a promising basketballer as a junior, and at 15, represented Australia in the 2018 FIBA Under-15 Oceania Basketball Championships, averaging 9.2 points, 3.7 rebounds and 3.2 assists across the tournament collecting a gold medal in their final against New Zealand.
[1] As a junior footballer, Windhager was the SMJFL 2019 Under 16's Division one Best & Fairest winner and second in the goalkicking table with 23 majors from 10 games playing for Beaumaris, including a bag of 11 against Bentleigh.
[2] Windhager was a member of St Kilda's Next Generation Academy, a pathway for indigenous and multicultural footballers who are typically under-represented and clubs incentivised with draft concessions.
Windhager was tipped to be a top 30 pick at the 2021 draft, but suffered a back injury late in the year.
In the later half of 2022, Windhager was used as a tagger on players such as Tim Kelly and Cameron Guthrie, and in round 22 received a Rising Star nomination for keeping Brisbane player and Brownlow medallist Lachie Neale to 16 disposals, while collecting 21 touches himself.