If Aaron Sorkin (The Social Network, The West Wing) was writing the story of Yahoo and he got to Marissa Mayer’s surprise entrance yesterday as Yahoo’s latest CEO, here’s how he would probably play it: the brilliant, tough, beautiful, charismatic engineer defies her Google glass ceiling and, through sheer vision and clever example, saves the pioneering Internet company. That’s how Sorkin would play it because he likes an underdog, loves smart, well-spoken people, and revels in beautiful if slightly flawed characters and happy endings. But in this case Aaron Sorkin would be playing it wrong.

To be clear, were I in the position of Yahoo’s board I would probably have hired Marissa Mayer, too. On paper she’s nearly perfect (only CEO experience is missing) and the drama of her going from not even on the list of candidates being discussed to getting the big job is wonderful theater that will play well on Wall Street for weeks, maybe months.  For once the Yahoo board seems to have been on the ball.

Still it probably won’t work.

Understand I have nothing against Ms. Mayer. I’ve met her only once and I’m sure she doesn’t remember me. I don’t know her. But I know about her and, more importantly, I do know Yahoo.

I can see why she’d want the job. It’s an epic challenge for someone who didn’t really have anywhere else to go at Google yet feels she’s destined for greater things. And I’m not here to say Marissa Mayer won’t achieve greater things in her career.

Just not at Yahoo.

Here we have a company in crisis. No, it’s worse than that: If companies had asses, Yahoo’s ass would be on fire. I knew that yesterday when I saw they had pulled founder David Filo into the position of spokesman. Filo, who is a nice guy and as nerdy as they come, is typically comatose in interviews, so whatever is happening in the executive offices at Yahoo has shot him full of fear-induced adrenaline for what would appear to be the first time in years, maybe ever.

This is it, I’m sure they’ve decided — Yahoo’s last chance to fix itself before the for sale sign goes up.

Yet Yahoo is still Yahoo and I’d put money on this old dog not learning enough new tricks to make a difference. It’s not that Yahoo has changed, by the way, but that it hasn’t changed.  It’s the world that changed around Yahoo. What worked so well in the Clinton years today barely works at all.

In our rock star CEO-obsessed business culture we believe that all it takes is the right guy or gal at the top with the right mojo to save the day. And on the short list of available charismatic leaders, Marissa Mayer looks pretty darned good.

That’s from the outside looking in. Inside Google Ms. Mayer had a reputation for being mean and not all that effective. She wasn’t in charge of that much and as time went on she was marginalized. She was employee #20 and the first woman female engineer but that didn’t make her a great leader or a visionary, just an early hire.

Now maybe Ms. Mayer was held back and never given a chance to shine. Or maybe people above her saw her deficiencies and kept her at a level where she could do no harm or could remain effective. Only time will tell.

This is one instance where I’d be happy to be wrong. I have no desire to see Ms. Mayer fail. I like underdogs and happy endings, too.

If Aaron Sorkin were to get a happy ending for his Yahoo story he’d need a few more elements that probably aren’t there. He’d need a subordinate character willing to risk all and act as a moral center for the company, demanding the new CEO do the right things.  He’d need his Marissa Mayer character to listen and learn. But most importantly for a Sorkin story he’d need a caricature antagonist, a powerful bully of a competitor unable to get out of its own way.

Yahoo might yet find the first two of these required components, but I know it doesn’t have the third.