The winner of an intriguing and tightly contested three-horse race for the competition's highest individual honour will be announced in Sydney on Tuesday night at the .
A new-look panel featuring former players, media, referees and technical staff voted on each of the 135 regular-season matches to decide on the recipient.
City pair Mooy and Fornaroli both boast head-turning statistics this season.
Mooy scored 11 goals from the midfield, laid on a league-high 20 assists and created 104 chances from 26 appearances, in what will surely be the in-demand 25-year-old's last campaign in Australia before a shift to Europe.
Meanwhile, Uruguayan strike sensation Fornaroli has already wrapped up the Golden Boot with his tally of 25 goals, and is already being widely hailed as the league's best-ever import.
Castro has been another picture of vision and skill.
The Spanish attacker was the driving force behind the Glory's rampant comeback from the table's depths to secure a finals place, with 13 goals to complement partner in crime, striker Andy Keogh.
Dark horses for the gong include Brisbane duo Jamie Maclaren and Corona, and Western Sydney's Mark Bridge and Mitch Nichols.
There are a string of genuine contenders for the W-League's Julie Dolan Medal, including Welsh star Jess Fishlock and Matildas co-captain Lisa De Vanna of Melbourne City.
A-League coach of the year is also up for grabs, with several strong contenders including Kenny Lowe (Perth), John Aloisi (Brisbane), Guillermo Amor (Adelaide), John van't Schip (Melbourne City) and Tony Popovic (Western Sydney).