Max King kicked four goals as the well-organised Saints proved far too slick with their speed and ball movement in a comfortable 16.10 (106) to 5.10 (40) victory on Friday at RSEA Park.
Cooper Sharman, Jack Higgins and Tim Membrey kicked three goals each, while former Port Adelaide defender Riley Bonner and first-round draft pick Darcy Wilson impressed.
But the Saints' convincing performance was soured by Windhager's injury, which puts him in doubt for the season opener against Geelong on March 16.
It was almost a year to the day since Windhager broke his opposite hand in the corresponding fixture last pre-season.
"It's just a little break in his other hand so we're still hopeful he'll (play in) round one," Saints assistant coach Robert Harvey said.
"It's disappointing for him but it's nothing serious. He's had a great summer so we're looking forward to getting him back for round one.
"He'll be able to run still and keep fit but it's just a minor setback."
Wilson was St Kilda's top pick at last year's draft and showed signs he could slot straight into Ross Lyon's first-choice team with an eye-catching display against Essendon.
"He's fitted in really well. He's got a great attitude and he gets out what he puts in," Harvey said.
"To see him and Hugo Garcia come in and do some stuff for us - and Liam Henry from another club - was really good to see and I think that will excite the fans."
The Western Bulldogs also suffered an injury blow when former cricketer James O'Donnell went down with an ankle injury early in their 25-point practice match win over Hawthorn at Whitten Oval.
No.6 draft pick Ryley Sanders showed why he is among the early Rising Star contenders with an impressive performance for the Bulldogs, immediately looking comfortable at senior level.
Hawks recruit Mabior Chol sent a scare through the camp when he had a shoulder injury assessed but showed promising signs in his first competitive hit-out for his new club.
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