Fast-growing online video site Whistle Sports has lined up a big new teammate, announcing a $7 million investment from European satellite-TV powerhouse BSkyB this morning in London, part of a larger Series B round of fundraising for the sports-oriented site, which already counts among its early investors such star athletes as Derek Jeter, Peyton Manning and Tim Wakefield and tech/TV heavy hitters Bob Pittman (AOL, iHeartMedia) and Geraldine Laybourne (Oxygen Media, Defy Media).

The latest funds will help the company expand its sales force; grow its international presence, especially in Europe; and grow its presence on YouTube, where it already has 8.5 million subscribers to 192 sports-oriented channels, said company CEO and founder John West. The BSkyB investment is only part of the company’s Series B round of venture capital investment. Other partners will be announced subsequently.

Sky’s interest in Whistle Sports is part of the UK giant’s ongoing program of investing in innovative startups, and follows recent investments in online video aggregator Pluto.TV, and ad tech firm Sharethrough. It also has stakes in streaming box maker Roku, Jaunt and 1 Mainstream.

John West Whistle SportsWhistle Sports is one of a small group of tightly focused multi-channel networks on YouTube and other platforms that have emerged in the 18 months as serious players in the online video space, said Peter Csathy, president of Manatt Digital Media, which consults with many companies in the space. Those MCNs have become serious acquisition or investment targets for traditional media companies hoping to reach Millennial and younger audiences that depend more on mobile and social platforms to find and talk about entertainment. Traditional media outlets such as network television and their advertisers have had a hard time reaching these avidly sought young audiences.

That’s why deals such as the Whistle Sports investment are important, Csathy said. They give media companies “a chance to learn about the space. They can learn about the company, learn about the management. If they like what they see, they can swoop in and make sure no one else gets it. The game is increasingly being played in the media world on the smallest screen you can find. If you’re a media company and have to monetize yourself, you want the broadest cross-media platform possible. (With deals like this, traditional media companies are) getting access to where the kids are. It’s still early stages, so you know you have to be there.”

A spate of acquisitions by big media companies the past year have taken off the table major “horizontal” multi-channel networks that represent a broad range of online video creators, including Maker Studios, AwesomenessTV and Fullscreen, Csathy said. What’s left are a set of fast-growing companies focused on popular “vertical” subject areas such as fashion, dance, Spanish-speaking audiences and, in Whistle’s case, sports.

Whistle is adding 150,000 subscribers a week on its video distribution platforms, which so far include YouTube and the Xbox 360’s Xbox Live service, said West. All told, the company reaches about 24 million users across seven platforms.

“What we’ve done in last few years is figure out where today’s generation are consuming video-based content,” said West. “It’s short-form content designed to augment live (broadcasts of) sports. We’re sort of at the intersection of Millennials and (the succeeding) Generation Z, depending on your definition.”

The company already has deals with the NFL, Major League Baseball, and the professional Lacrosse league, among other initiatives, and is increasingly organizing its content across verticals such as football, baseball, basketball and lacrosse. Opening a London office recently and staffing it with a YouTube Sports veteran has provided an opportunity for the company to dive more deeply into soccer (football in the rest of the world), cricket and other sports popular in Europe and beyond, West said.

Sky Sports is Europe’s leading multi-platform sports broadcaster and home to English Premier League football, Formula 1, International Cricket, International Rugby and European and U.S. Tour Golf. The relationship with Whistle Sports will offer the potential to collaborate on content creation and to share talent across both networks, Sky said today. It also allows for exploring innovative promotional opportunities aimed at introducing the respective brands — and their content — to new audiences.

One hot area is instructional videos for young athletes. There are surprisingly few pro athletes with their own YouTube sites (the Los Angeles Lakers’ Jeremy Lin is one prominent exception), but those few athletes figure prominently in Whistle Sports plans, West said. Athlete channels on the site include pro Frisbee player Brodie Smith and Dude Perfect, which features a group of athletes specializing in trick shots of all sorts.

Here’s the most recent Brodie Smith YouTube video, featuring a series of trick shots recorded during a visit to Istanbul, Turkey: