"It was a disappointing way to mark my 50th cap because I felt I let myself down," said the Glasgow hooker in his column in the Scotland on Sunday.
"I take responsibility for problems in the lineouts, and they were a shambles in the first half. The South Africans worked hard and they contested it well, but I feel we were just a bit slow on the ground and gave them too many hints as to where we were going, but we did change it at half-time, and it was a lot better, and we won a lot more ball in the second half."