Speaking to The Sun, Stuart revealed that show bosses had originally planned to leave the door open for Michelle should she decide to return to Weatherfield in the future.
But they soon changed their tune when the more dramatic option reared its head.
“It was a big call killing her off,” Stuart said, “especially after I promised Michelle I wouldn’t.
“But the writers came up with this massive story. So you have to go, ‘OK, there won’t be any other Michelle Keegans, but new people will emerge’.”
Michelle previously admitted she had been “gutted” when she learned of Tina’s fate, but later came to terms with it, saying: “I’d rather go off with a bang than in a black cab.”
Michelle filmed her final scenes for the soap last week.
Tina’s murder will air at the end of May, with the identity of her killer being kept such a closely guarded secret that four different versions of the storyline have been filmed.
Michelle’s first post-Coronation Street job will see her join ITV’s Lorraine Kelly as one of the judges of her show’s High Street Fashion Awards.