NEW YORK (TheStreet) -- Past criticism of Yahoo! (YHOO) and its CEO Marissa Mayer aside, Mayer's move to build Yahoo's own daily fantasy sports versus buying a company deserves a hat-tip -- not to mention doing it so quickly as to let people use the product before the NFL season starts.

Those unfamiliar with the daily fantasy sports (DFS) space might want to listen to this podcast I recorded a couple of weeks ago with Adam Krejcik of Eilers Research. In it, we discuss how it's the fastest growing section of the gaming world today, even though technically it's a skill-based endeavor. The two most recognizable companies in this space are DraftKings and FanDuel, which are bombarding the airwaves with TV ads to attract users.

Both DraftKings and FanDuel are private and have raised a boatload of venture capital to this point. Don't be surprised to see them go public soon. Because they're new and trail-blazing the DFS space -- and trying to keep pace with each other -- they are spending money like crazy to attract new customers.

And therein lies the genius of what Yahoo! has done.

Instead of spending a Tumblr-sized amount of money to buy FanDuel or DraftKings (Yahoo! spent $1.1 billion in cash and stock in 2013 to acquire Tumblr), Yahoo! has built its own product. I'm certain the cost of building its own product was far less than the over $1 billion it would have cost to buy either FanDuel or DraftKings.

Yahoo!, despite all the criticism it takes, is still a monster in sports and fantasy football. It's been one of the most popular fantasy football sites for years. Those players are typically casual but passionate. They draft their teams at the start of the year, follow the season intensely to see how they're doing, make updates to their teams and revel in the glory of winning or laugh at their losing friends.

In short, all those customers beating a path to Yahoo!'s door are prime target customers for daily fantasy sports. And Yahoo! -- unlike FanDuel and DraftKings -- spends little to attract them. Yahoo! simply advertises to them once they're there -- there's no need to blow a billion dollars on ads on Walt Disney's (DIS) - Get Report ESPN to acquire customers.

Amaya, which owns Poker Stars, has said it will also enter the market for DFS by the fall, while ESPN had said it would partner with DraftKings in the space, but then backed out of the equity deal.

The daily fantasy sports arena is heating up and no clear winner exists. Yahoo! may not take over the number one spot in the space, but this is a smart and cheap way for them to grab some growth over the next few years as daily fantasy sports explodes.

This article is commentary by an independent contributor. At the time of publication, the author held a long in Yahoo.