Willey, 26, hurt himself while playing for Yorkshire during England's T20 Finals Day on Saturday and an X-ray on Sunday suggested he could have suffered a significant injury.
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He will undergo a further scan and be assessed by a consultant on Monday. He has been withdrawn from England's ODI squad until the extent of his injury is known.
Willey's place in the squad will be taken by Nottinghamshire seamer Jake Ball.
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The England squad will convene in Southampton before the first match of a five-match series at the Rose Bowl on Wednesday.
The Test series between the countries was drawn 2-2.
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