Robinson said after last week's 15-13 win at Michigan State that he rolled an ankle late in the game.
The loss of Robinson, who rushed for 629 yards and five TDs, shrinks what's already a slim margin of error for the eighth-ranked Hawkeyes, who rank 86th in the nation in scoring offense.
Iowa (8-0, 4-0 Big Ten) will replace Robinson with fellow freshman Brandon Wegher, who has for 321 yards in relief of Robinson this season. Iowa hosts Indiana on Saturday.
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