"Going to the other side of the world is one thing, coming back and doing well as well as she is expected to is very hard".
Jockey Hugh Bowman pulled the trigger with 600m to go and Winx powered home to win by almost two lengths from the Godolphin raider Benbatl.
"That horse is a bit better runner than any she's faced in the last three years".
"It's the reason she is here now going for a fourth Cox Plate".
Winx, the world's greatest thoroughbred, has created history by winning a record fourth consecutive Cox Plate.
Winx had looked relaxed at the barriers before the race, and she was settled quickly in fourth or fifth behind early leaders D'argento and Benbatl.
"We will all sit down and talk about her future in a few weeks, " Waller said.
There is no need to retire Winx now as it is too late in the breeding season for her to be served by a stallion but it is expected she will race on next autumn with her farewell race highly likely to be the Queen Elizabeth Stakes at Royal Randwick during The Championships in April.
"I'd say with time and treatment he'll be right and be able to come back, we'll just have to see".
Winx continued her dominance at Moonee Valley on Saturday.
OVER 1000 punters arrived track-side at Ferguson Park this afternoon for the Cox Plate Day races.
Winx is a seven-year-old now and seemingly defying time, racing at an age most mares have been retired to the breeding barn.
"That is why we are so lucky with Winx because her owners bought her to race and because she is in the form that she is and she is happy to race, they (owners) are happy to continue to do so".