David Carr at QB after Alex Smith injured

David Carr has taken over at quarterback for the San Francisco 49ers after Alex Smith suffered an apparent injury to his left shoulder during a big hit Sunday.

The 49ers and Carolina Panthers are tied, 10-10.

Smith started quickly, finding tight end Vernon Davis for a 53-yard gain and, soon after, for a 1-yard touchdown. The passing game has lacked rhythm more recently, however. Smith completed 9 of 19 passes for 129 yards and an 87.4 rating before Panthers defensive end Charles Johnson sacked him.

Carr attempted one pass (it fell incomplete) before the 49ers punted. Smith's return was initially listed as questionable.

The 49ers have shown little confidence in Carr to this point. Making a quarterback change without benching Smith gives them an opportunity to see if things improve with another quarterback under center.