See: Jason Campbell, Oakland. Campbell -- helped by a devastating run-game performance -- had a career-best passer rating against the Broncos last week, just days after a career-worst showing against San Francisco.
Coach Mike Singletary cited Smith's leadership as one critical reason behind the decision.
"Talking about Troy Smith, he was the starter in Baltimore until he was sick, and I don't want anyone to forget that. He is a pro football quarterback," said Denver defensive coordinator Don Martindale, alluding to the player's bout with tonsillitis late in the 2008 preseason that eventually led to Joe Flacco earning the No. 1 job with the Ravens.
"He sits back in the pocket, he's strong, he's' got a good arm; he's accurate. What his plus is is that after all that, if things break you down, he can hurt you (on the ground). He's not a scrambling quarterback; he's a pro quarterback that reads coverages and does a nice job and is accurate with his balls that he throws. Then you add on the fact that if things break down, he can run with it."
One positive for Denver is that it should have the core of its secondary Sunday to defend Smith. Both safety Brian Dawkins and cornerback Andre' Goodman will be back, which allows Nate Jones to slide back to his normal nickel role.
The only absence on the back end should be rookie Perrish Cox, who was starting in Goodman's place but suffered a concussion against the Raiders.
"He's competitive and a damn good quarterback," said Broncos defensive lineman Justin Bannan, a former teammate of Smith's in Baltimore. "People are going to start seeing what he's all about pretty soon."
The first comparison that comes to mind among Denver's previous opponents that rival Smith is Tennessee's Vince Young, for his dual-threat abilities.
But Bannan feels Smith is "a lot better thrower ... He's got a cannon for an arm and can put it anywhere all over the field."
Still, the 2006 Heisman Trophy winner from Ohio State last started a game in 2007. He played in only four games last season, completing five of nine passes for 24 yards and an interception. He signed with San Francisco in early September and was selected over David Carr, who mopped up for Smith last week in a loss to Carolina.
Given that layoff, expect the Broncos to mix up their coverages and try to disguise them to the last possible second to make the quarterback think quickly and perhaps bait him into mistakes on obvious passing downs.
Denver studied tape of Smith's Ravens' days to get a feel for the player but believe San Francisco won't alter its offensive approach much to compensate for Smith's absence. San Francisco has tried to push the ball more to receivers like Michael Crabtree and Josh Morgan under new coordinator Mike Johnson.
At the same time, Denver has to be cognizant of Smith's mobility in scheming against the 49ers.
"We're going to have to defend him a little differently than some other people that we play," Broncos coach Josh McDaniels said.
SERIES HISTORY: 12th regular-season meeting. Broncos lead series, 6-5. Teams last met in 2006, when the 49ers knocked the Broncos out of the playoffs with a Week 17 win at Invesco Field at Mile High, 26-23.
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