SAN FRANCISCO — Next Sunday night, the 49ers' secondary will face MVP candidate Tom Brady on the New England Patriots' chilly home field.
But first, the 49ers will host a less-decorated AFC East quarterback: Miami Dolphins rookie Ryan Tannehill.
It's a calm-before-the-storm scenario, and it could generate swift momentum for the 49ers' secondary, arguably the club's most stable unit.
Dolphins coach Joe Philbin applauded those 49ers defensive backs this week regarding their role in Aldon Smith's league-high 17? sacks.
"The secondary helps (No.) 99's production because they do such a great job covering," Philbin said. "Sometimes the quarterback doesn't have real good places to go with the ball quickly, so he holds onto it at times and here comes the pass rush."
The 49ers (8-3-1) have allowed the second-fewest passing yards in the league (189.0 per game). That's quite a feat considering they've matched up against four of the league's 10 most proficient quarterbacks: The Packers' Aaron Rodgers, the Saints' Drew Brees, the Lions' Matthew Stafford and the Giants' Eli Manning.
While opposing quarterbacks change weekly, the 49ers have fielded virtually the same secondary since early last season: Cornerbacks Tarell Brown, Carlos Rogers and Chris Culliver; safeties Dashon Goldson and Donte Whitner.
They've officially played 26 consecutive games together (including playoffs). That's produced a bond extending off the field, such as their Thanksgiving feast at Brown's house.
"A lot of guys are close," Goldson said. "We hang together outside of here and crack jokes."
But their on-field unity and maturity is what counts most.
Defensive coordinator Vic Fangio pointed to a key benefit of the secondary's familiarity: "It's the communication, both the spoken word and the unspoken word, because sometimes you can't always speak out there."
Yes, Fangio's defensive backs at times have relied on body language instead of his astute play calls.
"We just really read our body language, and sometimes we just feel certain things," Culliver said. "It works in our favor."
Will those bodies be healthy enough to withstand Brady's barrage of passes in a week, much less whatever Tannehill throws at them Sunday?
On Wednesday, the 49ers' top three cornerbacks surfaced on the injury report: Brown was out with a hamstring injury while Rogers had a knee issue and Culliver an illness. The prior week's injury report included Goldson (ribs, calf) and Whitner (knee).
Brown, who's started every game at right cornerback since last season, has battled knee and hamstring injuries to his left leg. He practiced Thursday in a limited capacity and was a full participant Friday.
"It was nagging, and I just needed a day off to let my body heal up and I'll be ready to go on Sunday," Brown said Friday.
Since arriving as a rookie last year, Culliver has seen Brown and Rogers battle through other ailments. "I know them," Culliver said. "They'll battle it out and they're always going to play."
Brown and Rogers rank as the league's top cornerbacks in tackling efficiency, according to ProFootballFocus.com, which lists Brown with one missed tackle and Rogers with none. Culliver ranks among the top 10 cornerbacks in several categories, including fifth in yards allowed per cover snap (0.72) and seventh in catch-rate allowed (46.2 percent).
Unlike a year ago, the secondary's production can't be measured by interceptions. Goldson has a team-high three, Culliver two and Whitner and Brown one apiece. Rogers, who had a career-high six last season, has none. That group produced 19 interceptions last season.