The toughest puzzle to solve in the NFL might be who your quarterback should be. Your backup quarterback.
Recent history is filled with teams that floundered after starting quarterbacks got hurt or just plain stunk. The No. 2 guy came in and couldn't play a lick.
Pittsburgh and Arizona are down to the third string and it hasn't looked pretty. Ben Roethlisberger went out with shoulder and rib problems and both veterans in reserve, Byron Leftwich and Charlie Batch, have flopped.
The Cardinals have been through John Skelton, veteran backup Kevin Kolb, Skelton again, and now rookie Ryan Lindley, who looks overwhelmed. They've gone from 4-0 to 4-7.
Look at last season's Bears, who were playoff bound at 7-3 when Jay Cutler went down. In came Caleb Hanie and out the window went any postseason hopes.
Jason Campbell wasn't very effective during November this year when Cutler was sidelined by a concussion. Next thing you know, Chicago's big lead in the NFC North started shrinking.
Sometimes, though, a team has the right guy as the backup, usually a veteran who can handle the limited role, but is ready to step in when needed. Matt Hasselbeck in Tennessee and Chad Henne in Jacksonville fit that bill.
And sometimes a team has a No. 2 who should be the No. 1, which apparently is what Jim Harbaugh believes in San Francisco.
In a gutsy move for a team with legitimate Super Bowl aspirations, Harbaugh has anointed second-year QB Colin Kaepernick to guide the 49ers even though the incumbent, Alex Smith, has fully recovered from a concussion. While Harbaugh likes to claim he has two starters, he's made it clear where his preferences are by keeping Smith on the bench even though Smith was playing particularly well before getting hurt.
"I think we have two very good quarterbacks, that it's a unique situation," said Harbaugh, who should know something about the position having played it in the pros and also coached Andrew Luck at Stanford. "You have two guys that you feel can win, have won for you. Two guys that deserve it. Two guys that have earned it, Alex over a long period of time, Colin by merits of the last three games."
It's a dangerous game Harbaugh is playing, especially if he needs to go back to Smith at some point. Such controversies often divide teams, especially when a long-time starter who has had success and was not slumping loses his job through injury.
But Harbaugh looks at Kaepernick's athletic skills, strong arm and remarkable savvy for a second-year player, and he sees potential greatness. He apparently doesn't forecast the same greatness for Smith.
Former 49ers coach Steve Mariucci, who worked with Hall of Fame QB Steve Young, then with Brett Favre in Green Bay, marvels at the quick development of Kaepernick considering how little practice time backups get.
"It's a luxury to have a veteran backup because he has played before and he knows pro defenses and hopefully has been in your system for a few years," said Mariucci, now an analyst for NFL Network. "And he doesn't require a lot of reps in practice. He can be ready without taking up a lot of practice time, because there is very little practice time in the NFL. So it's nice to have a guy who's been through it and practiced these things before.
"With a youngster you are rolling the dice, he is learning while pretty much watching, and hopefully he does not have to play. But you see Kaepernick, it's interesting to see that and to see how many young quarterbacks are playing in the league."
Mariucci believes the second-string quarterback has one of the most challenging jobs in football, made particularly difficult if he is replacing a superstar. Sometimes that works, such as Matt Cassel's performance with New England when Tom Brady wrecked his knee in the 2008 season opener — the Patriots went 11-5, although they didn't make the playoffs.
Most of the time, though, it's an utter failure. Look back no further than to Hanie, or to the group that replaced Peyton Manning last year in Indianapolis.
Backup QBs must have specific traits.
"He better have a terrific work ethic and spend as much time in there as a starter, learning and asking questions and being mentally ready," Mariucci said. "Take a mental rep every time the ball is snapped. He'd better show his teammates he is willing to put in the time to be as ready as possible.
"There are no dodos who are backups, they have to be smart guys, a sponge, and absorb as much as they can without physically going through it on the field."
Rich Gannon lived on both sides of the QB equation. He went from backup after being drafted in the fourth round by New England in 1987 — but catching on with Minnesota — to a starter, then to a backup again in Kansas City. After he became a starter with the Chiefs he moved on to become a league MVP and Super Bowl quarterback with the Raiders.
He wonders if the position is getting proper instruction.
"I don't believe some teams do a good enough job coaching the position," said Gannon, now a host on SiriusXM NFL Radio. "Is it a guy who is in quality control rather than full-time (coach)? Not a lot of quarterback coaches have played the position, although some quarterback coaches are very good — Mike McCarthy never played quarterback and might be one of the best.
"It's also hard to develop a backup when you are changing coordinators year after year. Look at Brady. Charlie Weis left, Josh McDaniels took over, then Josh leaves and Bill O'Brien comes in, and now Josh is back. But it the same system around the quarterbacks.
"But changing systems, how do you develop the guy who starts and the guys behind him? You're never able to build on what you did the year before, and it has hurt the development at that position."
Gannon is a perfect case of a sub who became a standout starter. Kaepernick could be the next example. Regardless, Gannon insists teams must be willing to address the backup QB spot with an open mind.
When he was with the Chiefs, he told general manager Carl Peterson during contract negotiations not to "grind over $75,000." His reasoning was simple: Gannon was an insurance policy, and maybe no one wants to pay policy premiums, but what happens when you need to use that policy?
"You've got a playoff team," Gannon said. "Do you really want to roll the dice with a guy who hasn't done it or would you rather have a guy with a lot of reps? That is the reality today, with a lot of teams that are rolling the dice."
The 49ers included, but in an unusual way.
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