As if the battle for your viewership on Sunday nights wasn't already in full swing, two networks -- one a longtime leader in must-watch programming, the other not known for original content -- just upped the ante with two new entries making big waves.

Salem casts a spell for WGN

(Credit: WGN America)

When WGN (a subsidiary of Tribune (NYSE:TRCO)) announced it was getting into the original series space, many were skeptical of how it might compete with established rivals. Concerns spiked higher when the network announced its debut effort, Salem, would bow on Sundays ... arguably the most jam-packed night of the week. But the show -- and the network -- are off to a great start.

The show's 10 p.m. premiere had 1.5 million total viewers, 647,000 of them falling in the coveted 18-49 demographic. Even more impressive is that represents a 600%+ gain over the network's usual adults 18-49 numbers (season-to-date) and is now its highest-rated telecast since 2007. Including encores that number rose to 2.3 million viewers and 886,000 from the demo.

Salem was originally developed for FX, but was moved to WGN after FX's American Horror Story went the "witch" route in its third iteration, Coven. Starring Janet Montgomery (Made in Jersey) and Shane West (Nikita), the 13-episode first season represents just the first of a number of projects in the WGN pipeline, including Manhattan, centered on the development of the Manhattan Project, and a retelling of The Ten Commandments (with top filmmakers Gus Van Sant and Lee Daniels attached).

While 1.5 million may not sound like much in comparison to shows airing on broadcast networks, it's a big deal. For WGN to score right off the bat puts it in a strong position to grow an audience and lure advertisers, and it's entirely possible that number will go up when time-shifting numbers come into play. pointed out that back in 2007 when AMC used Mad Men to launch its original series slate, its 18-49 audience was just a little over 500,000 ... which means Salem's success could be the start of something big for WGN.

Silicon Valley develops into hit

(Credit: HBO)

Over on pay cable, a few weeks ago HBO (a subsidiary of Time Warner (NYSE:TWX.DL)(NYSE:TWX.DL)) debuted Silicon Valley, the network's latest attempt to launch a comedy during its successful Sunday night original programming block. Now after only three episodes, executives have just renewed the show for season 2, possibly breaking a long streak of misfires. Longtime viewers know that despite a rich history of big name laughers including Entourage and Curb Your Enthusiasm, HBO has had a rough go of it recently with such niche attempts as Enlightened and Hello Ladies failing to make an impact.

Silicon Valley started off big (by cable standards) with 2 million viewers and became the best debuting HBO comedy since 2009 when Hung launched. While in subsequent weeks it's slipped in the ratings, it still commands more viewers than a number of the network's previous flops. The series could have easily gone in the opposite direction -- it doesn't have any big name actors and it's targeting a rather specific demographic. But Valley has crossover appeal and its quirky style worked in its favor.

The series also gives its group of young comedic actors material that plays to their strengths. Every part is well casted and there are no weak links in the ensemble. Audiences were already intrigued due to the involvement of Office Space's Mike Judge and once they saw Valley mixed his trademark humor with an interesting concept, they were hooked.

As a result, HBO now adds another weapon to its comedy arsenal, which to this point only included Girls (which some refuse to acknowledge as a comedy), Looking (ditto Girls), and Veep, which itself has slipped in the ratings. Still Veep is fronted by Julia Louis-Dreyfus, a big bold-faced name for HBO and the winner of the last two Emmy awards for Best Actress in a comedy. Given the show's critical appeal, it wasn't a surprise that HBO reupped Veep at the same time it announced Valley's pickup this week.

With Dwayne "The Rock" Johnson's Ballers and the Tim Robbins/Jack Black starrer The Brink also expected to be on the network's 2014 slate, HBO is positioned for a balanced back half that its rivals should be worried about.