The champion horse had to do it tough. She was seven lengths behind the race lead with 500m to run.
She still had work to do, needing to come from half a length behind Le Romain at the 200m.
Winx then exploded at the 200m mark to win by almost a full three lengths in another incredible moment of racing history.
"She's just colossal," McAvaney said.
Trainer Chris Waller said: "She's just very, very special.
"She's the star."
Winx last galloped to victory in August, snapping Black Caviar's record of 25 straight victories, and becoming just the 14th horse to win 30 or more times in a career.
Winx's trainer Chris Waller confirmed to The Daily Telegraph earlier in the week the champion mare would need another run before she chases an unprecedented fourth successive Cox Plate.
"Her run beyond Saturday is not locked in yet,'' Waller said.
"It is likely to be in Melbourne but we haven't given up on keeping her here.
"She can go two weeks, four weeks, where ever she goes. I said at the end of last preparation it is one run at a time and we will stick to that."
