Mike Blair has made a late withdrawal from the British and Irish Lions' tour match against Western Province on Saturday.
The Scotland captain was named on the bench as cover for starting scrum-half Harry Ellis.
But he sprained a ligament in his foot during training on Friday and will now miss the game at Newlands.
With Mike Phillips still recovering from the midweek victory over the Sharks, Wales wing Shane Williams - who has played at number nine earlier in his career - will take Blair's place among the replacments.
The Lions are targeting a fifth successive victory as they build towards the first Test against world champions South Africa in Durban on June 20.