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When one franchise changes its starting quarterback only a week before the season begins, and another pulls the plug on its starter after the opening game, it's a pretty good signal that it might be an unusual year at the game's most critical position.

Less than a month into the 2007 season, it certainly has been, with four teams already having started two different quarterbacks in their first three outings.

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And with more changes on the way.

Since the opening week of the season, there have been seven quarterback switches, including two in which injured players who had been forced to sit out a game regained their status atop the depth chart. And those changes don't count the monumental decision in Jacksonville, where coach Jack Del Rio dumped former first-round selection Byron Leftwich and turned to David Garrard a week before the season began.

Nor does the number factor in the nine in-game replacements that have been made to date, moves that didn't necessarily precipitate a switch of starters.

"I think to be so early in the season and have this kind of change already, it's remarkable, really," said one longtime offensive coordinator whose team has considered a change but has yet to make one. "You just don't see it as this level. Or, at least, you didn't. But it seems now like [coaches] aren't so reluctant anymore to bring out the hook. There's so much pressure, and every win means a lot, right? So if it means hurting a [quarterback's] feelings by yanking him, but you get a [win] out of it, hey, why not?"

There will be at least two changes this weekend -- with journeyman Brian Griese supplanting the struggling Rex Grossman for the Chicago Bears, and rookie Trent Edwards taking over for the injured J.P. Losman in Buffalo. More are probably on the way. Injuries to starters in Carolina (Jake Delhomme) and Oakland (Josh McCown) will likely force changes. In Minnesota, it's all but a given that Kelly Holcomb will start a second straight game for the injured Tarvaris Jackson.

But injuries are a natural part of the attrition process at quarterback. It's become a rarity when a quarterback survives an entire 16-game schedule. With a few exceptions -- like the historically durable Brett Favre, Peyton Manning and Tom Brady -- the concept of the iron-man quarterback has become about as passé as the single-wing formation.

What has made things different recently at the position is that coaches are making so many quarterback switches out of choice, not necessity.

In what was viewed as a watershed event for the Jaguars, Del Rio didn't even wait for the season to start. The Cleveland Browns awarded the starting position to Charlie Frye after a long training camp competition, were waxed by the Pittsburgh Steelers in the season opener, and decided they had seen enough. Not only did they bench Frye, but they traded him to Seattle for a sixth-round draft choice just two days after the opener and installed Derek Anderson as the caretaker until rookie Brady Quinn is ready to play. The Bears have benched Grossman, the guy who led the team to a berth in Super Bowl XLI just seven months ago.

Time was when a coach would view the kinds of metamorphoses enacted in Jacksonville and Cleveland as traumatic. Now it seems coaches are taking drastic steps in an effort to stop the hemorrhaging before it begins. Everyone wants stability at quarterback. But what they want even more are wins, and coaches are doing what they feel is best for their teams to get them.

"I think everyone here likes and respects Rex [Grossman], and realizes that what's happened with our offense certainly isn't all on him," Bears wide receiver Bernard Berrian said. "But we need some kind of spark. You don't want to get so far behind [in the division] that it's too late to do something about it."

Projecting forward, teams such as Atlanta, Kansas City, Oakland and perhaps Miami are all candidates to have changes that are basically a function of performance and not injury. And while Arizona officials continue to insist that second-year veteran Matt Leinart is their guy, the fact that coach Ken Whisenhunt has installed a no-huddle package and will use two-time league MVP Kurt Warner to preside over it raises questions about the Cardinals' starting situation.

In 2006, there were five quarterback changes that were coaching decisions. For the 2005 season, there were nine. But in the five-season stretch from 2000 to 2004, the average number of quarterback switches not related to injury was 4.4. And so the propensity for change definitely has increased and the trend has continued into the current season.

Which certainly could result in an increase in the number of quarterbacks who start at least one game in 2007.

There were 50 different starters in 2006, down by five from the year before that, and the lowest number since 2001. But the trend so far this season points toward a dramatic upswing again. during 1996-2005, the average number of starters was 57.

But with coaches far less reluctant to shake things up anymore, it looks like the number of starters in 2007 will easily surpass that average.

Len Pasquarelli is a senior writer at ESPN.com.