It's an unspoken rule, probably written by a player, that a starter shouldn't lose his job to injury.
Try selling that line to Pittsburgh Steelers fans who are busy chatting up rookie quarterback Ben Roethlisberger as the second coming of Terry Bradshaw.
Since replacing Tommy Maddox in Week 2, Roethlisberger has led the Steelers to four consecutive wins. Maddox, who was annoyed when his team used a first-round pick on a quarterback, should take his time recovering because the throne now belongs to the heir apparent.
Then there are the Buffalo Bills, who have a budding controversy in their backfield.
With Travis Henry on the limp, Willis McGahee got his first NFL start on Sunday and was impressive enough against a good Miami defence to get the talk shows humming.
Not only did McGahee put up with his team's first 100-yard rushing effort of 2004 (111 yards), the Bills actually won.
So what to do?
The precedent for the spurned injured star already exists in New England where Drew Bledsoe lost his starting job to Tom Brady three years ago. The Pats have won two Super Bowls, while Bledsoe has suffered in Buffalo.
In Pittsburgh, the solution would appear to be simple.
Barring a drastic reversal of form, there's no way Roethlisberger is going anywhere.
A hero has been born and a handful of restaurants in the Steel City are already serving Roethlis-burgers in honour of the man leading their 5-1, AFC North-leading team.
"I can't say enough about him," Pittsburgh coach Bill Cowher said following Sunday's dramatic 24-20 comeback win in Dallas.
Cutting through the hype, the win over the Cowboys may have been Roethlisberger's most impressive work to date.
Not only did Big Ben complete 21 of 25 pass attempts, he was 11 for 11 on the Steelers' final two scoring drives.
As he has done each week in his brief pro career, the 11th pick overall out of Miami of Ohio has shown experience beyond his 23 years.
His teammates have praised him for his poise and his ability to scramble out of trouble. At 6-foot-5, 240 pounds, he's tough to tackle and has a better arm than the two quarterbacks drafted before him, Eli Manning and Philip Rivers.
Prior to this past Sunday's game, Dallas coach Bill Parcells hailed Roethlisberger as the most impressive rookie quarterback he had seen since Dan Marino.
You should know that most coaches are prone to such platitudes in the days prior to a game. The Patriots' Bill Belichick, for example, would have you believe that every opponent is the second-coming of the 1972 Miami Dolphins.
Parcells generally avoids the B.S. As gutted as he was on Sunday, he stuck to his assessment.
"I haven't changed my mind on him," Parcells said. "He's the real deal. He's out of the pocket throwing 50-yard passes right on the money."
The situation in Buffalo is a touch more delicate. Henry, who is expected to return next week, is a legitimate lead back in his own right and other than the occasional dose of fumble-itis, he has had a reasonable career as a Bill.
But remember that Buffalo general manager Tom Donahoe drafted McGahee in the first round in 2003, a move that was met with some criticism given the team's many needs. Donahoe needs to get validation soon and McGahee certainly seems capable.
The easy answer is to split the duties for now. A team could always use a pair of good running backs, after all.
Not so at quarterback. Maddox learned it in 1992 when he was drafted by the Denver Broncos as a potential replacement for John Elway. Things didn't work out for Maddox then and it doesn't look promising this time around either.