Turns out Alex Smith himself was just as confused.
"It was definitely my first question: 'What's changed?" Alex told the San Francisco Chronicle. "That was definitely something that was on my mind and (Coach Singletary) made it very clear that was his thinking, that we're going into this game and I gave us the best opportunity. He made the decision, I'm going to get ready to play. We're all going to get ready to go play."
Singletary offered that Alex's superior knowledge of the 49ers' playbook is behind the move. "I think right now we need everything that we can possibly have. Everything we learned in training camp, the offseason - we need that.", Singletary told the Sacramento Bee.
Troy Smith, who I guess does not know the playbook as well, was 3-2 as the 49ers' starting quarterback. Alex Smith, who I guess knows the playbook up and down, is 1-6 as the 49ers' starter.