A large-scale repositioning of regional sports networks by cable and satellite carriers is gathering speed and impact, and it is now involving two of the country’s largest media markets.

After a short-term extension of a prior carriage agreement with Comcast, the Mid-Atlantic Sports Network completed a new contract with Comcast, the largest cable carrier in the Washington-Baltimore region, which includes the country’s No. 9 and 29 media markets. But the deal carries a major shift: The Orioles-controlled MASN will move from Comcast’s most basic cable tier to a more expensive and less broadly distributed “Ultimate TV” tier.

That change will mean that those wanting to see the Orioles and Nationals in that region will eventually need to pay an extra $20 per month. Comcast is phasing in the switch with a six-month promotion that offers its “Popular TV” customers the ability to transition to “Ultimate TV” for three months with no additional charge, with a $10 surcharge for months four through six.