Last July, I said the only thing Marissa Mayer hadn’t changed since becoming chief executive at Yahoo (YHOO) was the logo. Two months later, she changed that, too.

After overhauling all of Yahoo’s key properties, acquiring dozens of Internet firms, and breathing new life into one of the most beat-down companies in tech history, what does Mayer have to show for it? Far less than she’d hoped.

Sure, the stock has had an impressive run, but that’s almost entirely due to co-founder and former CEO Jerry Yang’s strategic investments in Chinese e-commerce giant Alibaba and Yahoo Japan.

And while Internet traffic at some of Yahoo’s sites is up, revenue from its core business – search and display advertising – are heading in the opposite direction. And it doesn’t help one bit that competitors Google (GOOG) and Facebook (FB) are showing impressive gains, particularly in mobile.

A few weeks ago, Mayer fired the guy she handpicked to reinvigorate ad sales, COO Henrique De Castro. That’s when much of the tech media began to pick up on the idea that Silicon Valley’s favorite fashion-forward executive may have run out of tricks. Me, I saw this coming a mile away.

When Yahoo’s famously foul-mouthed former chief executive, Carol Bartz, outsourced the company’s search technology to Microsoft (MSFT) in 2009, I was floored. The last thing I expected was for Bartz to dump what I thought was the “critical growth engine” that Yahoo desperately needed to turn itself around.

I understand why she did it. By outsourcing search to Bing, Bartz cut her enormous R&D budget while maintaining 88% of her search advertising revenue stream (Microsoft gets the remaining 12%). But it never made sense to give up on what was arguably the most important core technology and potential differentiator Yahoo had.  

Hasn’t Google clearly demonstrated that the web revolves around search? That the more online content and commerce there is, the more important it is for users to be able to find what they’re looking for?  

Google’s monetization of search – primarily via its AdWords search advertising platform – is the most brilliant business innovation of the Internet age. It’s made Google the second most valuable company in America. It’s the web’s equivalent of Microsoft’s ubiquitous PC operating system, Windows.

Having run Google’s search business in a prior life, Mayer knows this all too well. And last Friday’s news that Yahoo had struck a deal to bring Yelp’s local listings and reviews to Yahoo search results is Mayer’s first public move to differentiate the company’s search results from partner Microsoft and get back into the search game. It’s smart, it’s the right thing to do, and it’s probably the only strategy that can get the Silicon Valley company growing again.

While Mayer has previously compared her search business strategy to that of wineries buying grapes from independent vineyards, that’s probably just an attempt to spin her way out of a situation she’s not the slightest bit happy with, as some have reported.

It’s no secret that Mayer wants out of the 10-year Microsoft agreement, but that’s not going to be feasible anytime soon, considering that it accounted for nearly a third of the company’s revenue last quarter. And while there are conditions that would allow Yahoo to exit the deal, that’s not likely to happen until 2015, when either company can opt out.

In the meantime, the company has hoards of engineers and a few high-ranking executives working on two high-priority internal programs, code named Fast Break and Curveball, intended to relaunch what may very well be Yahoo’s only significant opportunity for revenue growth – search.

It’s a big bet but, to Mayer’s credit, it’s the right bet … and a winnable bet. I happen to think that search is still in its infancy, meaning there’s a lot of innovation to come and disrupt the market. No, Marissa Mayer is not out of tricks yet.

Steve Tobak is a management consultant, executive coach, columnist, and former senior executive. He runs Silicon Valley-based Invisor Consulting where he advises executives and business leaders on anything and everything. Contact Tobak.

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