Following news of a family bereavement, Procter left the squad's Cardiff base on Tuesday night.
A club statement read: "Luke Procter will miss the final day of the ongoing County Championship fixture against Glamorgan
"Procter left the squad on Tuesday evening following news of a family bereavement.
"The thoughts of everyone at Northamptonshire County Cricket Club are with Luke and his family."
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It means Northants will effectively have to play the final day of the match with just nine players.
Gareth Berg was ruled out of taking any further part on Monday morning after suffering an ankle injury in the warm-up.
Glamorgan went into the fourth day of the Group Three encounter with a first innings lead of 247 runs.