Samson Lee will miss Wales' clash with Scotland on Sunday after failing the final stage of the return to play protocols.
The Welsh tighthead suffered a concussion last weekend against England but had initially been cleared for the Six Nations clash at Murrayfield.
However the WRU have today announced that he has not come through the final stage of the return to play protocols and therefore will not be available to face the Scots.
Aaron Jarvis comes into the starting lineup to replace him, while Cardiff Blues tighthead Scott Andrews moves onto the bench.
Lee has established himself as first choice for Wales since taking over from Adam Jones during last June's tour to South Africa.
After missing out on the squad for the Six Nations, Jones announced his international retirement, leaving Wales a little short with the Scarlets prop now out of action.