Yahoo! CEO Marissa Mayer will face a $10 billion decision in a few months thanks to her company’s stake in Alibaba.

Judging by comments made Wednesday at a conference hosted by TechCrunch, she might want to plop down a good part of that windfall on a mobile startup.

“[Mobile is] a really critical issue,” Mayer said on stage at the conference. “It’s certainly one of the biggest missed opportunities that I saw when I came here.”

While she has already made many changes since taking over nearly two years ago, all the deal-making and internal shuffling may be just a prelude to her biggest test — what to do with proceeds from the Alibaba IPO.

The sale is expected to intensify the pressure on Mayer to revive Yahoo!’s revenue growth after years of lethargy.

As Mayer has previously acknowledged, the Internet company’s future may be all about mobile.