The 34-year-old has suffered a recurrence of the shoulder injury that ruled him out of the 30-22 defeat to Scotland on March 8.
He returned for the meeting with Ireland last weekend, the 25-24 reverse in Cardiff, which was intended to be his home farewell.
The 35-cap hooker announced his intention to retire from the international scene at the end of the current RBS 6 Nations competition.
He only returned to the Wales fold for last month's meeting with England after almost four years in exile.
Humphreys took over the captaincy following the departure of Colin Charvis after the shock 30-22 loss to Italy in the competition opener.