Grant Cohn: Colin Kaepernick's diminishing returns (w/video)

Colin Kaepernick is in the tank. Every week he sinks a little deeper.

I picture him diving into a pool like Dustin Hoffman in “The Graduate,” swimming to the deep end, sitting cross-legged on the bottom, covering his ears and screaming inaudible gurgles while Simon and Garfunkel sing “The Sounds of Silence.”

Let’s put the plunge in context.

Kaepernick is 27 years old and declining. Every season he’s in the NFL his passer rating gets worse. In 2012, his rating was 98. In 2013, his rating was 91. And this season, his rating is 85.

Did Kaepernick peak early?

The quarterback the 49ers dumped for Kaepernick - Alex Smith - is 30 years old and improving. His passer rating this season is 92, the best rating he ever has had 13 games into a season. He still hasn’t peaked.

Let’s take the comparison further. The past two seasons, Kaepernick has played with Anquan Boldin - a future Hall-of-Famer, a go-to wide receiver. Smith has played with no go-to wide receiver. The Chiefs’ best receiver is a running back, Jamaal Charles.

With that in mind, compare Smith’s stats to Kaepernick’s stats since the beginning of the 2013 season.

KAEPERNICK: 88.4 passer rating, 59.5 completion percentage, 37-18 touchdown-to-interception ratio.

SMITH: 90.5 passer rating, 62.7 completion percentage, 39-13 touchdown-to-interception ratio.

Despite throwing to inferior receivers, Smith outperformed Kaepernick in every statistical category. Imagine how much bigger the gap between Smith’s numbers and Kaepernick’s numbers would be if Smith had Boldin and Kaepernick didn’t.

This isn’t to say Smith is a great quarterback - he certainly is not great. He has flaws. Of course the Niners would be better off with Peyton Manning or Aaron Rodgers instead of Smith or Kaepernick.

But Smith is better than Kaepernick - that’s a fact. The 49ers kept the wrong quarterback - that’s a fact.

Not only is Smith better than Kaepernick, Smith is a better fit for the 49ers.

When a team has a terrific defense - and the Niners have a terrific defense - all the team needs is a quarterback who won’t mess things up. That perfectly defines Smith, not the mute guy.

Smith is like Troy Aikman. Aikman didn’t mess things up. His career passer rating was pedestrian - 81.6. Smith’s career rating is 82.4. The most touchdown passes Aikman ever threw in one season was 23, which also happens to be Smith’s single-season career high.

Kaepernick messes things up - it’s what he does. He can’t even get the ball snapped fast enough to beat the clock.

And he has developed a pattern. Almost every game, it seems his first pass either is intercepted or almost intercepted. The Raiders picked off Kaepernick’s first pass a few days ago - Kaepernick threw the ball right to the defender, hit him in the chest. It’s like Kaepernick expects to throw interceptions and fulfills his destiny right away.

Kaepernick is covered in a cloak of self-doubt. It hangs over his head and his face wherever he goes. The man is freaked, petrified. I’ve never seen someone play quarterback in such fear.

Compare Kaepernick to Derek Carr, a 23-year-old rookie.

Kaepernick never will be as poised as Carr is now. Nothing bothers Carr, the kid who calmly points downfield and shows receivers where to run as chaos surrounds him in the pocket.

Everything bothers Kaepernick - the media, the fans, the haters, the pressure, the trash talk, you name it.

Harbaugh tried to boost Kaepernick’s confidence a few weeks ago, tried to pull Kaepernick out of the tank by calling him “Great with a capital ‘G.’” But that didn’t work. Harbaugh couldn’t pull Kaepernick out of the tank. Kaepernick is too far down there.

Alex Smith never went in the tank, never had the emotional problems Kaepernick has. Smith lacked confidence, but that changed as soon as Harbaugh came to the Niners. Smith needed a head coach who believed in him, who supported him publicly. Harbaugh did that, and Smith’s career took off.

Harbaugh never had to lie and call Smith great just to pump him up. The highest praise Harbaugh ever gave Smith was to call him a Pro Bowler, which he is.

Harbaugh constantly has to lie for Kaepernick. This past Monday, Harbaugh characterized Kaepernick’s regression as a “rough patch.” This is not a rough patch. This is falling into the Grand Canyon.

This is where a reporter asked Harbaugh if Blaine Gabbert is going to start the next game, and the question was asked seriously. When you’re at the Blaine Gabbert level, it’s no rough patch.

The biggest problem on the 49ers is Kaepernick. Bill Walsh always said the quarterback defines the limit of the offense, and Kaepernick diminishes that limit weekly.

We used to think of Smith as Steve DeBerg, the place-holder, and Kaepernick as Joe Montana, the franchise savior.

But Kaepernick was Steve DeBerg all along.

Grant Cohn writes sports columns and the “Inside the 49ers” blog for The Press Democrat’s website. You can reach him at grantcohn@gmail.com.