Sheridan Smith has been forced to withdraw from her leading role in West End show Funny Girl for up to four weeks because of "stress and exhaustion".
Understudy Natasha Barnes will replace the 34-year-old Cilla star.
Natasha has stood in for the past three performances that Sheridan has missed this week, including one on Wednesday night.
In a tweet, the producers of the show said: "Sheridan Smith will be taking a leave of absence from Funny Girl due to stress and exhaustion.
"The entire team at Funny Girl is thinking of Sheridan, and know she is getting the rest and support she needs during this difficult and stressful time."
The statement continued: "We will all miss her enormously and send her our love and best wishes - and we are looking forward to her return to the show in due course."
Sheridan first missed a performance on Monday, the night after the Baftas TV ceremony.
She had hit out at suggestions in the media that she had not taken well to her failure to secure the Best Actress award.
Suranne Jones took home the Bafta for Doctor Foster, while Sheridan had been nominated for her role as cancer blogger Lisa Lynch in The C Word.
On Twitter, she accused the press of "bullying" and was supported by her fans.
She tweeted: "When will u stop bullying? I had the best night in memory of my girl @LisaLynch."
The Mrs Biggs star tweeted an apparent reference to her absence on Monday: "Well done press! U let down me, the cast & everyone who spent money to see me. I apologise. Profusely!"
The tweet continued: "Sorry! Sorry I'm not strong enough."
The Savoy theatre said Sheridan was "indisposed".
The opening monologue by Baftas host Graham Norton appeared to contain a joke at Smith's expense.
He quipped: "We're all excited for a couple of drinks tonight. Or, as it's known in theatrical circles, a few glasses of 'technical difficulties'."
It came less than two weeks after a performance of Funny Girl was cancelled halfway through, which producers said was down to "technical difficulties".
Sheridan had earlier denied speculative reports in the press that the show had to be stopped early because she had been drinking, with a spokeman saying the allegations were "categorically not true".
Funny Girl is showing at the Savoy until October 8.