SANTA CLARA, Calif. -- The San Francisco 49ers have signed free agent quarterback David Carr to a two-year deal.

General manager Scot McCloughan said Monday that Carr will help provide depth at quarterback.

Coach Mike Singletary has repeatedly said 2005 No. 1 pick Alex Smith is the starter, but didn't rule out signing an experienced quarterback who could push Smith and challenge for playing time.

Carr, an eight-year NFL veteran, was the top draft pick in 2002 out of Fresno State. He spent the past two seasons as a backup to Eli Manning with the New York Giants.

The 49ers on Monday also agreed to terms with Detroit on a trade that would send quarterback Shaun Hill to the Lions. The 49ers would receive an undisclosed 2011 draft pick in return.