WA star Jason Behrendorff struck with the first two balls of the match, including the wicket of Test hopeful Cameron Bancroft, to stun the Dragons.
Alex Hepburn went about rebuilding the innings to make a patient 60 and helping Willetton recover with 202 all out.
Kallen Bond also made 45, while some later-order hitting from veteran Brad Hogg (41 from 68 balls) also helped lift the Dragons after their disastrous start.
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READ NOWSimon Mackin took the wicket of Anthony Murphy late on, to leave the game on a knife-edge, with Subi 1-33 in reply after 10 overs.
Play resumes on Saturday at 11.40am.