Long a low-rated night for the CW, the net is planning to radically alter how it does business on Sundays.

Word emerged late Thursday that The CW is close to sealing a deal with an as-yet unnamed media conglom to take over the night. By Friday morning, speculation centered on Media Rights Capital, the indie shingle that’s already starting to make a splash in the TV world.

Under the proposal, the CW would sell the 7 p.m. to 10 p.m. block to MRC – which would partner with an advertising conglom. Both would turn around and develop programming and sell ad time.

Insiders said the MRC deal wasn’t signed, however, and could still fall apart. CW announces its fall sked on Tuesday, which means both sides are working furiously to strike a pact.

In some ways the plan is a throwback to the early days of TV, when advertisers were more involved in programming primetime. More recently, UPN initially sold the slot for “WWE Smackdown” to World Wrestling Entertainment as a time buy.

Time buys have become the norm on Saturday mornings, where nets like NBC and Fox have sold their Saturday morning kids blocks to outside companies. The CW will do the same thing beginning this fall, when 4Kids takes over the block that had been Kids’ WB.

Decision to sell the Sunday primetime block is an acknowledgement that the night has been a tough one for the CW – and before that, the WB, which also struggled to gain ratings traction there.

Deal would allow the CW to focus its attention on Monday through Friday nights. CW has been looking to create more weekday flow on its sked, and believes it will be able to do so after “Smackdown” departs its lineup at the end of September.

Time buy also allows the CW to maintain a presence on Sunday nights, rather than give the night back to affils.

The CW could not be reached for comment.

MRC, headed up by Modi Wiczyk and Asif Satchu, has already lined up several series commitments and pilots for broadcast and cable this upcoming season. Industry vet Keith Samples is president of MRC TV.

MRC’s is already backed by the advertising world: WPP (which operates media buyers such as MediaCom) is an investor. Company is also bankrolled by Goldman Sachs, AT&T and investment fund D.E. Shaw.