Wales centre Gavin Henson has been ruled out Saturday's Test against South Africa due to an Achilles injury.
The centre, who has only played three games since returning from ankle surgery, made the decision to withdraw himself after being able to take only a limited part in training during the week.
"Gavin decided to tell us after the training session that mentally and physically he was not going to be ready for the game," said Wales tactics coach Rob Howley.
"We wanted to leave that decision down to Gavin Henson. He's a mature enough person to make that decision.
"The problem has been niggling him and he wanted to be 100 percent, and he's obviously not feeling 100 percent.
"It's been a six-day turnaround before an international. There are high demands on players and Gavin has fallen foul of them."
Henson will be replaced by Tom Shanklin in Wales' starting line-up, with Jamie Roberts switching to inside centre to accommodate Shanklin in his favoured outside centre role. Andrew Bishop steps up to take a place on the bench.