SANTA CLARA — The San Francisco 49ers will have four new starters in their secondary for Sunday's season opener, and not one of them started a game for the team last year.
Three of them weren't even with the Niners in 2010. But the revamped unit has worked well together this summer and is eager to take on the responsibility that comes with holding up the back end of San Francisco's defense.
"It's on us as a secondary," strong safety Donte Whitner said Friday after the 49ers conducted their final practice before hosting defending NFC West champion Seattle. "We understand that we're going to have to play well to make sure our defense is a really good defense."
San Francisco finished 24th in the NFL last season in passing defense. Whitner is one of two former high first-round draft choices the 49ers brought in as free agents this summer to upgrade the unit, joining left cornerback Carlos Rogers as the new leaders of the secondary.
Another newcomer, veteran Madieu Williams, is likely to start at free safety in place of Dashon Goldson, who hasn't practiced since last week due to a sore knee and has ruled himself out of Sunday's game.
Tarell Brown is slated to start at right cornerback in place of Shawntae Spencer, whose string of 32 consecutive starts in San Francisco's secondary is in jeopardy.
Spencer recently returned to practice after missing most of training camp and all four exhibition games with a hamstring injury. Brown was San Francisco's nickel back last season and has been playing with the first unit since mid-August.
"We need that group to play well together and that will be an important unit in this game," coach Jim Harbaugh said.
"You strive to have them all working in tandem. It's important that they're all on the same page and they're all communicating," he added. "That's so important on the back end."
Whitner, selected by Buffalo as the No. 8 overall pick of the 2006 NFL draft, has taken on the lead role as quarterback of the unit and will call out plays for the secondary.