Amid rumblings that Marissa Mayer's turnaround plan for Yahoo has all but failed, the CEO wants investors to know that she is overseeing one of the fastest growing businesses in Silicon Valley.

During a quarterly earnings call Tuesday, Mayer highlighted her company's success at monetizing its mobile, video, native and social products since 2012. 

"In 2014, these businesses accounted for more than $1.1 billion of GAAP revenue," Mayer said. She added that in the coming year, these offerings will "contribute over a billion and a half dollars to our business," up from next to nothing two years ago, when Mayer arrived at Yahoo. 

"If broken out on their own as a company, they would undoubtedly be one of the fastest growing startups in the world," she said.

To put those numbers into context, Yahoo's forth quarter revenue was down two percent to $1.8 billion, which was below analysts' expectations.

Still, Mayer indicated that this high-growth "startup" within Yahoo represents the future for the company. Prior to the call, it had been difficult to judge whether some of Yahoo's recent acquisitions had been worth the price paid. But Mayer attributed much of Yahoo's success in the realm of social media and native advertising to Tumblr, which Yahoo acquired in 2013. 

Mayer cited a November GlobalWebIndex report that said Tumblr had surpassed Instagram as the fastest growing social network over the preceding six months. In the fourth quarter of 2014, its audience grew 9 percent, according to Yahoo's metrics.

The biggest news for Yahoo's shareholders came when Mayer announced at the beginning of the call that it will spin off its nearly $40 billion stake in Chinese e-commerce company Alibaba. 

Going forward, Mayer said she wants Yahoo to be seen as a "preferred acquirer" but said that should wouldn't consider acquisitions as large as Tumblr -- which Yahoo paid $1.1 billion for -- unless the deal closely aligns with its mobile, video, native and social business (a group Mayer referred to throughout the call by the new acronym "MaVeNS").  

During a live blog of the call, Re/code's Kara Swisher, commented that after the spin-off is complete, Mayer wouldn't be able to "afford the companies that would truly change the game for Yahoo."

Despite the fact that some still see Yahoo's Q4 results as evidence that the company cannot be jump-started, Mayer repeatedly emphasized her optimism. 

"In closing, we are all here to return an iconic company to greatness," she concluded.