Anna Faris' shock Mom departure a 'nightmare' for the show

Anna Faris has mysteriously quit the hit TV show she's starred in for seven years – and the bombshell has created a "nightmare."

Faris abruptly left sitcom Mom last week, only days before production was set to begin on Season 8.

A source close to the show has spoken out on about her shocking exit.

"It was a surprise to hear that Anna was leaving. None of us are happy about that," a source told People magazine.

"It was sudden and unwelcome, and it left the entire network scrambling. This is not a good thing at all."

The popular show first premiered in 2013. Faris played single mum Christy who is reunited with her dysfunction mum, Bonnie (Allison Janney), when she least expects it.

"Mom has been one of CBS is more profitable scripted shows, in a very challenging economic time," the source explained.

"And now one of the leads is gone. It's actually a nightmare. No one wanted this."

After announcing her departure, Faris thanked her co-workers for "a truly wonderful work experience" on the series.

"The past seven years on Mom have been some of the most fulfilling and rewarding of my career," she said.

"I'm so thankful to Chuck, the writers, and my amazing castmates for creating a truly wonderful work experience. While my journey as Christy has come to an end, allowing me to pursue new opportunities, I'll be watching next season and rooting for my TV family."

The actress will reportedly be written out of the show during season 8.