Fast-growing online sports video site Whistle Sports has wrapped up the rest of a big Series B round of funding, pulling in $28 million from mostly European media companies alongside previous investors. Company executives declined to disclose the resulting valuation, but said the valuation percentage was “probably pretty traditional.”

The company previously had disclosed that European satellite giant Sky Broadcasting would be one of the big partners in this round, chipping in a quarter of the total. This round’s lead investor is Emil Capital Partners, an affiliate of the giant German holding company the Tengelman Group. Other backers include Liberty Global, the Euro-focused cable arm of Liberty Media, along with additional funding from previous backers who include pro athletes Peyton Manning and Derek Jeter.

The three-year-old company has been growing fast, building on a YouTube multi-channel network with a tight focus on creators in the sports vertical. Those creators make short-form videos about a wide range of athletic pastimes, designed to entice Millennial audiences that aren’t watching traditional sports programming as much.

The company also has built a strong presence on Facebook and other social-media platforms that collectively display its content to 50 million followers, though the company acknowledges there’s a great deal of overlap among users who follow the site on multiple platforms. The company is also expanding onto new video distribution platforms beyond YouTube, first with Microsoft’s Xbox 360, with Roku, Apple TV and the Xbox One to come.

The company has built partnerships with several prominent sports leagues, including the NFL, Major League Baseball, NASCAR, the PGA Tour, Major League Soccer, two pro lacrosse leagues, the AVP pro volleyball circuit and the Harlem Globetrotters. Content partners include prominent video star Dude Perfect, Australian rules footballer Brodie Smith and Jeremy Lin, the NBA Los Angeles Lakers guard.

“It’s a fairly nascent category, largely because of the (video) rights issues,” said CEO John West. “We’re coming at it with a sports theme, and having league partnerships has been valuable in unlocking (those rights problems). We feel like we’re building a social sports network.”

The company did an $8 million Series A funding round in 2012. The new round will finance the company’s expansion into Europe, particularly in the high-profile soccer (football) markets there and elsewhere outside the United States. It will invest in more content creation, particularly in specific sports, recruit and support more content creators and increase its ad-sales operations.

Whistle Sports now has relationships with nearly 240 channel partners that collectively have about 12.5 million YouTube subscribers. That makes it smaller than the big “horizontal” MCNs such as Maker Studios, Fullscreen and AwesomenessTV that have been involved in so much acquisition news over the past year, but West said the narrow focus may be an advantage as the online video business continues its shockingly rapid evolution.

“What we’ve seen in the last six months is that YouTube was the dominant player, but now there’s (competition from) Facebook, Twitter with Amplify and Vine,” West said.

As Whistle Sports evolves away from a strict dependence on YouTube, the company is now generating about half its revenue from branded content. A recent partnership with the U.S. Archery Association with Dude Perfect generated 11 million impressions on Facebook alone, West said, and 180,000 shares in the first week after it was posted. The MCN remains a vital place to generate revenue, and cultivate video talent, and also has become a powerful channel for marketing out to a big Millennial audience.