Sports fans are a fickle bunch. Beat a favored opponent in a playoff game and next thing you know they want to put your name on the building. Lose a nail-biter, and you better hope stadium security ate their Wheaties that morning.

Forty-niners quarterback Alex Smith knows this all too well today. After a legendary showing against Drew Brees and his Saints, in which he looked for all the world like a Super Bowl hurler, Smith looked helpless Sunday evening against the Giants. He completed fewer than 50 percent of his throws and was a shocking 1-for-13 on third down conversion attempts.

But which Smith is closer to the real Smith?

Entering the season, Alex was a measly 19-31 in his career as a starter. No one from the coaching staff to the bleachers believed a lick in him. But under the supportive eye of former quarterback and new Niners head coach Jim Harbaugh, the veteran Smith seems to have blossomed and realized some measure of his potential.

Smith threw the fewest interceptions of any starting QB in the NFL in 2011, and the Niners led the league in turnover differential. This level of ball control gave the Niners the advantage in terms of time of possession and field position in virtually every game they played, and contributed to their 13-3 record and number two playoff seed.

The 2005 first overall draft pick showed signs of real brilliance throughout the year. He led the 49ers to four victories in which they were down in the fourth quarter, the most impressive being his two come-from-behind touchdown drives in the last few minutes against New Orleans. Also notable was his performance in Week 4 in Philadelphia, in which he notched over 200 yards in the second half.

But it’s no secret that the real heroes of the season were the defense and place kicker David Akers, whose 44 field goals on the season set an NFL record. Why did he get so many chances? The Niners offense converted on just 40 percent of their red zone appearances, actually down by 7 percent from just a year ago.

Then there are games like Sunday or like Thanksgiving Day in Baltimore when Smith just seemed flat-out flustered. He’s uncomfortable in the pocket and inaccurate with even short-to mid-range throwing plays. How many times Sunday did he overthrow a receiver downfield or fling it right at the ground, apparently doing his best Tebow impression?

The bottom line with Smith is he’s inconsistent. Can he lead the 49ers to a Super Bowl victory? Of course. The way he out-dueled the newly-minted single-season passing champion, he can do anything on any given Sunday.

Will he? That’s a different question. Any single game can go either way, but there is no reason to believe he can string together three or four victories against other great football teams.

Harbaugh won’t give up on his pet project easily, and Smith will be the starting quarterback when the 2012 season gets up and running. A full training camp and offseason will do him good and the good citizens of Northern California will be rightfully filled with hope.

But the NFC West is getting a lot better. Seattle finished the season on a 5-3 run and Arizona’s secondary will continue to grow as cornerback Patrick Peterson develops. San Francisco could easily see a lot more competition inside the division next year.

Smith has earned another chance to nail down his job long-term, but the team has to be willing and able to make a change when the moment is right. And needless to say, if the opportunity to trade for Peyton Manning were to present itself, the Niners would be foolish to consider the position “occupied.”

Alex Grotewohl can be reached at [email protected].