The network will continue to operate under the ROOT Sports brand and will provide year-round coverage of the Mariners as well as other professional, college and high school sports programming.
The agreement provides that the network will televise the Mariners through the 2030 season and increases potential revenue that can be used to bolster the team's player payroll.
Steve Greenberg, a member of the New York investment bank Allen & Company that advised the Mariners on the transaction, said the move will help the club compete financially in the evolving Major League landscape.
"All five clubs in the American League West now have long-term TV deals in place for many years," Greenberg said, "and the Mariners are in a better position than some of their rivals and actually competitive with all their rivals within the division. We believe that's an important milestone to have achieved.
"MLB clubs that own a substantial stake in their own [regional sports networks] tend to be among the strongest and most stable franchises in the league."
DIRECTV Sports Networks president Patrick Crumb noted that "from a viewer perspective, there really will be no visible change."
But the financial aspect of the agreement puts the Mariners on more-equal footing with teams like the Angels and Rangers that have reworked their own deals in recent years, which is why the club has been pursuing such a partnership since late 2010, according to Bob Aylward, Mariners executive vice president of business operations.
"It gives us the ability to make the long-range planning that our competitors have been able to enjoy," Aylward said. "We'll now be able to compete on the same level. The intention of this organization and owners is to compete at all levels and make sure we have a product that gets us into the World Series and win a championship. This deal in itself doesn't do that, but it's a piece of the puzzle and we're delighted to have this to work with."
DIRECTV Sports Networks, which owns and operates two other regional sports networks based in Denver and Pittsburgh, assumes a minority position and will continue to oversee management of the Northwest network.
Since its inception as Prime Sports Northwest in 1994, ROOT Sports Northwest has gradually increased the number of Mariners broadcasts it provides each year to this season's high of 159 of the 162-game schedule.
ROOT Sports Northwest reaches approximately 3.2 million homes in the region. The network currently has relationships with the Sounders and Timbers professional soccer teams as well as Gonzaga University and West Coast and Big Sky Conference sports.
Crumb said the network is always looking to add sports programming and acknowledged he's talked with Chris Hansen, the man trying to bring the NBA back -- and potentially an NHL franchise -- to Seattle.
"I reside in Seattle and have had conversations with Chris," Crumb said. "I'd characterize those more as get-to-know-you conversations. They're more focused on obtaining approval to get a franchise and move to Seattle, but he's certainly familiar with our ROOT Sports Network. We were the former home of the Sonics. At a point where Chris is able, we'd certainly be interested in having those conversations and deciding if it makes sense."
The Mariners have raised concerns about a proposed NBA/NHL arena being built just to the south of Safeco Field regarding traffic issues, but Aylward indicated that was a separate issue from a potential television partnership.
"The Mariners have had conversations with Mr. Hansen, but not about TV rights," Aylward said. "So that is pretty cut and dried. In the matter of the Sonics, the Mariners concerns about the location of an NBA arena are pretty well documented. But that concern is only about location of the facility. In our new role, it's going to be in our best interest to have more pro teams in Seattle. The concern we have about location is not going to affect broadcast rights.
"We'll rely heavily on the pro sports market knowledge DIRECTV has. We believe the Sonics and NHL would potentially provide excellent programming. But there are a lot of ways to do those packages. Assuming things happen, we'll be there."