EXCLUSIVE: The revolving door at the struggling OWN: The Oprah Winfrey Network continues without slowing, and even without warning or public announcement. This time it has claimed one of Winfrey’s closest and most trusted executives, Lisa Erspamer. We’ve learned that Erspamer, EVP of production and development for the underperforming cable network, was let go yesterday after an 18-year tenure with Winfrey. We hear that the news was delivered to Erspamer while Winfrey was out of the country. (Oprah has been in India to interview Deepak Chopra for her new show Oprah’s Next Chapter.) We hear Erspamer didn’t even receive the news from Oprah personally. No public statement was made. Instead an internal ”Assistant to the Office of the President” email was sent around only to staff: one of those impersonal “we wish her well” announcements. “Lisa was shocked,” a source tells us. “She’d been in Oprah’s inner circle. She went on cruises and vacations with Winfrey. She’d worked for her for almost 20 years. Oprah had transitioned her to OWN personally.” UPDATE THURSDAY AM: We heard from an OWN spokesperson this morning, who said: “Oprah called Lisa Erspamer from India where she is shooting an episode of Oprah’s Next Chapter, and by mutual agreement they decided that it was time for Lisa to move on.”

When Oprah first brought her longtime producer Erspamer to OWN, Winfrey praised her as a “creative superstar”. Now we hear that Erspamer, who had been in charge of programming, is taking the fall for the network’s rough first year on the air. That includes the tanking Rosie O’Donnell daily talk show which Erspamer most recently was in charge of trying to fix. But it had been Oprah’s idea to bring Rosie to the OWN network “so why isn’t Oprah blaming herself for the show’s .3 rating?” one source complains to us. ”It’s a disaster.” The network just shook up the Rosie Show by replacing original executive producer Page Hurwitz with Shane Farley and overhauling the show’s set after less than 3 months of use. The Rosie Show got off to a decent ratings start with 500,000 viewers tuning in to its October debut. But quickly lost a large chunk of its audience and now averages only about 200,000 viewers.

Erspamer first joined Winfrey’s Harpo Prods. in 1994 and rose through the ranks to co-executive producer of The Oprah Winfrey Show. That’s where she was in charge of the highest-profile episodes, including the two-part Whitney Houston interview and the big Pontiac giveaway. Erspamer was summoned to OWN in January 2010, following the first major shakeup at the Harpo/Discovery Communications venture that saw the exit of president Robin Schwartz and the appointment as CEO of Christina Norman who exited later on. Erspamer’s move was somewhat surprising since she had no TV series or network experience. “Lisa has been a creative superstar,” Winfrey said at the time. “She’s brought fire and force to many of the incredible shows we’ve done over the years. I value her passion and sensibilities and trust her instincts and judgment. I know she’ll be a great fit with the OWN team.”

Erspamer’s title changed last July when Winfrey, originally chairman of OWN, also named herself CEO and chief creative officer in the wake of Norman’s exit, while Harpo Studios presidents Erik Logan and Sheri Salata became OWN presidents. In light of that, Erspamer’s position was changed from chief creative officer to EVP of production and development. Salata has been overseeing programming, along with Winfrey, and is expected to continue to do so.

OWN has soaked up some $300 million in investment funds by Discovery Communications but has largely failed to outperform the Discovery Health network it replaced. Heavily promoted entries like Mark Burnett’s reality series Your OWN Show, Oprah Presents Master Class, and Rosie have disappointed. The network’s best ratings news in almost a year came at the beginning of January when Winfrey’s new series, Oprah’s Next Chapter, posted all-time highs in its first 2 airings. But it, too, has since dropped significantly.