Half the population, it seems, want to fire a quarterback who is undefeated. Alex Smith is on the hot seat. Trent Dilfer's name has been mentioned in conversation.

Please, people.

The 49ers' offensive troubles are serious, but they're not Smith's fault. Or, at the very least, when you're assigning blame Smith would be no higher than fourth on the list, behind Coach Mike Nolan, offensive coordinator Jim Hostler and San Diego Chargers president Dean Spanos.

Lest we forget, Smith was moving steadily up the Quarterback Growth Chart last season and now abruptly appears to have stopped. Is that his fault? Did he really go backward after winning late season road games in Seattle and Denver?

Did he take regression pills in February or in April? That seems kind of odd.

Actually what went wrong in February and April wasn't Smith's fault. First, Spanos fired Marty Schottenheimer so late that his only viable option was Norv Turner, the 49ers offensive coordinator. Which left Hostler as Nolan's only viable in-house option to replace Turner — the former thus becoming Smith's third offensive coordinator in three years.

By April, the 49ers had a good draft to cap off a good free agent signing season and expectations about the team started to wander into the unrealistic. And all those nice qualifiers about Smith being "the youngest starting quarterback in the league" and "only beginning to learn the pro offense" went out the window.

All of a sudden the kid who was starting to blossom last December looks unsuitable.

It's impossible to overstate the impact of Turner's departure, although Nolan tried to on his radio show this week by pointing out that the 49ers offense last year ranked a lowly 26th. That's true — but it's also true the 49ers did not have much talent and the defense was so abysmal the offense never stood a chance.

The issue is bigger than play-calling. For a young quarterback, Turner's presence made a huge difference, not only in technique and tutoring but also in psychology and confidence. Having the guy who taught Troy Aikman how to get Super Bowl rings, a teacher who has been through the fire and speaks with authority — all of that was huge for Smith.

Frankly, it was also huge for Nolan. He could turn over the offense to Turner without a second thought while he busied himself with defense and running the team. Nolan would be less likely to overrule Turner because he didn't have nearly the offensive chops expertise. Like Smith, Nolan too is learning on the job, and needed a veteran like Turner — just like George Seifert needed Mike Shanahan.

Now the 49ers have Hostler, who holds one of the prime coaching jobs in the NFL only because Nolan gave it to him. Hostler doesn't come with independent, indisputable authority. He doesn't know 14,000 times more about offense than his boss Nolan, the way Turner did.

Hostler's main asset in getting the job was his relationship with Smith. That he provides continuity.

I'm sure Smith likes and respects Hostler — but it's a little like your big brother trying to dole out discipline while your dad is at work. It just isn't the same.

Smith is still the youngest starting quarterback in the league, in his third year (yeah, yeah, I hear you: "Joe won a Super Bowl in his third year!"... "Tom Brady won a Super Bowl in his second year!"). He came out of college early; he didn't come from a pro style offense. Now he's on his third coordinator in three years — usually the kiss of death.

Yet he is smart. He has skills. He has been composed late in games. The only reason the 49ers beat Arizona was because he used his instincts to scramble for 25 yards on fourth-and one.

With those kind of wheels, you'd think they would have utilized them the next week. But Smith didn't run and didn't move around in the pocket (unless he was about to get sacked). He has been under tremendous pressure. His receivers have dropped balls that were well-delivered. His tight end appears to be wearing an invisibility cloak. And he's facing defenses that know exactly what the 49ers are going to do.

None of those things are Smith's fault.

Nor is it his fault that with four downs at the opponent's 26-yard line, his coaches didn't have the faith in him to let him go for a touchdown. Didn't view it as an opportunity to bring a young quarterback one more step along.

If Smith senses that his coaches don't trust him, he'll shrink a bit more down the growth chart. If the talk about making a change gets serious, if the criticism gets louder, nothing is going to get easier.