Ugle-Hagan was a shining light with three goals in last week's upset loss to Essendon, which left the Bulldogs reeling with a 2-3 record.
But he will miss the important meeting with the Saints at Marvel Stadium on Thursday night.
St Kilda are also missing their spearhead after Max King was ruled out earlier in the week because of a knee injury.
Ugle-Hagan has been replaced by ruck-forward Rory Lobb, who has earnt a recall despite concerns over an ankle injury sustained in a reserves match last weekend.
Lobb has played just one senior match this season, missing more games through the opening five rounds than he did during his entire first year at the Bulldogs in 2023.
The former GWS and Fremantle tall will line up in attack for the Dogs as under-fire coach Luke Beveridge attempts to test out St Kilda's undersized defence.
Ugle-Hagan's withdrawal comes as another huge blow for the Bulldogs after they lost star midfielder Tom Liberatore, who is in concussion protocols and undergoing further tests following his dramatic on-field collapse late in the loss to the Bombers.
Oskar Baker has been dropped, while Riley Garcia and James Harmes have been recalled to bolster the Dogs' midfield.
The changes come with plenty of heat on Beveridge, who has again overlooked former All-Australian Caleb Daniel.
The diminutive midfielder, who has been listed as an emergency, is set to spend a second straight week in the VFL despite racking up 26 disposals in a solid outing at the lower level last week.
St Kilda spearhead Max King has been ruled out of the clash with the Western Bulldogs. (Julian Smith/AAP PHOTOS)
St Kilda spearhead King injured a knee during his side's heartbreaking one-point defeat to GWS in Canberra last round and failed a fitness test this week.
His absence opened the door for veteran midfielder Zak Jones to be recalled.
But there was no room in Ross Lyon's team for key defender Dougal Howard, who has been named as an emergency.
Howard returned from a hamstring injury in the VFL last week and is yet to feature at senior level this season.
Like the Bulldogs, the Saints also take a 2-3 record into Thursday night's contest.
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