Agar sustained the injury while fielding during Australia's five-wicket defeat against India, yesterday.
"Ashton injured his right little finger whilst fielding in the match last night," the team doctor Richard Saw said in a statement.
"Following the conclusion of the match he went for x- rays which have confirmed a fracture of the finger. He will return home to Australia and consult a specialist with a possibility of surgery," he added.
Adam Zampa is most likely to replace him in the fourth ODI in Bengaluru on Thursday.
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