He burned Carroll. The sequence was Bochy let Affeldt start the 8th to face Morgan. Roenicke lifts Morgan for Carroll. Bochy takes out Affeldt and puts in Romo. Roenicke then lifts Carroll for Kotsay. The offensive advantage of doing so is just slight (if any) that it can in no way out weigh the defensive issue. And it means you let either McGehee or Betancourt hit for themselves.