Warren Littlefield was NBC's entertainment chief during the network's long run as the home of Must See TV comedy on Thursday nights.

But he doesn't think there will ever be another Must See TV night for his struggling former network -- or any of its rivals. For one thing, the TV landscape has become increasingly segmented.

I think there's a lot of outstanding television out there today, Littlefield told TheWrap. It's just (that) the average household has 200 channel choices and it's spread around, he said, noting that at the height of Must See TV, a third of the country was watching NBC on Thursday night. That's just never going to happen again.

Littlefield has written an oral history of the Must See TV years, Top of the Rock: Inside the Rise and Fall of Must See TV, scheduled for publication in May.

He said that he doesn't envy current NBC entertainment president Bob Greenblatt or his rivals because the competition for eyeballs is only going to get tougher for broadcast networks. The former network exec said that it's an easier task for niche cable channels to bring audiences what they want.

When you're still in the broadcast business, you're still trying to reach tens of millions, Littlefield said. You're trying to still aim for a broader audience, and I think that's a more difficult task to spread yourself across that audience, connect with them, as opposed to a very, very small, pinpointed audience. Difficult to do.

Littlefield, who was booted out, as he puts it, from NBC in 1998, now operates the Littlefield Company. He told TheWrap he conducted more than 50 interviews for Top of the Rock, with Jerry Seinfeld; Jack Welch, former CEO of NBC parent company General Electric; Kelsey Grammer and cast members and producers from ER, Friends and Will & Grace among those contributing.

His former network, led by Greenblatt since Comcast took ownership of NBCUniversal earlier this year, is once again in fourth place among the major networks this fall season.

I have a lot of respect for Bob, and I think he's got certainly a big job ahead of him, Littlefield said. There's not a whole lot there that's working particularly well right now.

He has higher hopes for Smash, set to premiere in February. which revolves around the cast of a Broadway musical and stars Debra Messing. He calls the show's pilot wonderful. And midseason they have 'The Voice' to help bring an audience to that, he said. It's one piece of the puzzle at a time, but certainly it's going to be a difficult road for them, because they just don't have that many pieces, and in the new year, when they lose football, it will be even harder.