Season 8 of the CBS sitcom premieres Thursday
Allison Janney and Anna Faris in Mom
Allison Janney and Anna Faris on Mom
| Credit: Monty Brinton/CBS via Getty

Allison Janney and fellow Mom star Jaime Pressly are opening up about Anna Faris' exit from the CBS sitcom ahead of the season 8 premiere this week.

Janney, who plays Bonnie, the mom to Faris' Christy, told Entertainment Tonight that her costar leaving was "a huge loss."

"It's a huge loss for the show to not have Anna because she was part of creating a character, Christy, that everyone fell in love with, who was so lovable and warm and gullible and funny and we will miss her so much," said Janney, 60.

She continued, "I think I'll miss the most, for me, the relationship between Bonnie and Christy, even though that will still continue. But she won't be present. That's what I'll miss."

Anna Faris in Mom
Anna Faris in Mom
| Credit: Robert Voets/CBS via Getty

Pressley, who stars as Jill Kendall, said that with Faris' absence and the ongoing COVID-19 pandemic, "it's a whole different set right now."

"But I do want to say that it feels like she's still here because we do talk about the character all the time," continued Pressly, 43. "And [Janney's] character is always calling her or vice versa. We still hear the name, we still talk about her. She's not gone as far as we're concerned, and we all spent so much time together over the years and love each other and support each other and we all want each other to be happy, so we're happy for her and we miss her no matter what."

Janney also teased that the new season, premiering Thursday, will showcase more of Bonnie's relationship with her husband, Adam (William Fichtner).

"It's been actually fun because Adam, Bonnie's husband, we find that we have more time to discover our relationship and that we in fact do like each other very much," the actress said. "In fact, we think we're so good at being in a relationship that we decide we can give advice to other people in relationships."

"It is a show everyone still needs because it's a show about positivity and hope and relationships. We're so grateful that we get to continue telling the stories about these amazing women and all leaning on each other, and helping each other get through whatever life throws at them," Janney later added. "Women who are all striving to be the better version of themselves and trying to do it in recovery."

Faris, 43, announced in September that she would not be returning to Mom after starring as one of the main characters for seven seasons.

"The past seven years on Mom have been some of the most fulfilling and rewarding of my career. I'm so thankful to Chuck, the writers, and my amazing castmates for creating a truly wonderful work experience," she said in a statement at the time. "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."

A source close to the show told PEOPLE at the time that Faris' decision to leave the hit sitcom came as a shock to her Mom family.

"It was a surprise to hear that Anna was leaving," the source said. "None of us are happy about that."

A week later, Janney posted a behind-the-scenes video from her first day on set for season 8. In the short clip, she shared a glimpse at how the cast and crew are staying safe amid the pandemic with added precautions.

"Hi everyone, we are all back at Mom. It's our first day with the new COVID protocol," she said, wearing a protective face mask. "Everyone's here and it's a whole new territory, but we're excited for season 8 to begin."

Mom premieres Thursday at 9 p.m. ET on CBS.