**Update** On his weekly radio show this morning, Mike Singletary confirmed that Alex Smith will start Sunday's game against Seattle. He told KNBR's Brian Murphy that Smith's experience was the key factor in the decision and that the 49ers coaches felt he gave the 49ers "the best chance to win." He said Troy Smith "has done some good things" and said it was possible he would go back to Smith at some point this season. **
Alex Smith will be back under center for the 49ers' most critical game of the season, according to a report on NFL.com. Smith was 1-6 for the 49ers before going down with a separated non-throwing shoulder against Carolina in Week 7.
Coach Mike Singletary left room for a change at quarterback earlier today when, asked who would start Sunday against division co-leader Seattle, he said he was undecided and gave Troy Smith only a lukewarm appraisal. "I thought he did decent," Singletary said of Smith's 10-25 performance Sunday against Green Bay. "I thought he did OK. Decent performance."
Troy Smith has started every game since Oct. 31 and has gone 3-2 in that span. He made a splash in a 23-20 overtime win over the Rams on Nov. 14, leading a heroic fourth-quarter touchdown drive and finishing with 356 yards and a 116.7 passer rating. Singletary has praised Smith's leadership ability throughout his tenure as 49ers starter. However, he hasn't surpassed 200 yards in each of the last three games, and his passer ratings have been 51.5, 61.7 and 64.4.
Still, his overall passer rating of 80.2 is better than Alex Smith's of 75. The biggest difference in the two has been the willingness to throw the ball down field. Troy Smith has averaged 8.1 yards per completion. Alex Smith's average is 6.4 yards.
Offensive coordinator Mike Johnson has hinted in recent weeks that the offense is more restricted with Troy Smith, who only joined the 49ers on Sept. 6. "I think he knows the overall plays, but there are 350 pass plays in a playbook," Johnson said last month. "There's no way you're going to know every single detail about 350 plays without having gone through training camp. That's just not going to happen."
Alex Smith also is well-versed at working out of the shotgun formation and operating a spread-like offense, which is what he ran in college and what the 49ers dabbled with last year. Johnson studied the spread during a year off from coaching in 2008. With Frank Gore out for the season with a fractured hip, the 49ers might be better suited running a more wide-open offense with replacements Brian Westbrook and Anthony Dixon in the backfield.
Westbrook played in a West Coast offense in Philadelphia and is adept at catching the ball out of the backfield. Dixon, meanwhile, played in a spread system at Mississippi State. As a senior last season, he took most of his handoffs when the quarterback was in the shotgun.
Meanwhile, the 49ers' postseason hopes would be snuffed out with a loss to Seattle, the team that throttled them 31-6 in Week 1. In that game, Alex Smith failed to capitalize on two early chances for touchdowns - including over-throwing wide-open Moran Norris in the end zone - and threw two interceptions. One of them was returned 32 yards for a touchdown.
-- Matt Barrows