Cook out of second ODI
The skipper complained of tightness in his right groin on Saturday, with Alex Hales added to the squad as a precaution - pending further testing on the day of the ODI.
However, the left-handed opener was confirmed as an absentee on Sunday, with Eoin Morgan due to replace him as skipper for the fixture at The Riverside Ground in Chester-le-Street.
"Cook has tightness in his right groin and will be assessed ahead of the game tomorrow," the ECB confirmed via their official Twitter account.
England won the first ODI at The Oval on Thursday - clinching an 81-run victory on the Duckworth-Lewis method.
Hales, who could replace Cook in the batting order, has never represented England in ODI competition.
However, he has featured in 32 Twenty20 internationals, averaging 37.85.