Ex-EastEnders star Jacqueline Jossa was reportedly in the frame to assume the lead role in Our Girl before the decision was taken to axe the show.
Keegan was herself a replacement for EastEnders actress Lacey Turner, who appeared in the first series, and according to The Sun, the show was considering tapping up another star from the BBC soap for a potential fifth series.
"Jacqueline was a shoo-in to take over from Michelle in Our Girl but ultimately it would have been tough for her to commit to being away for so long," a source told the newspaper.
"Jacqueline knew it was a massive role for her but after the initial call it all went quiet and nothing more was said.
"With the pandemic and restrictions on filming, they felt it was best to just pull the plug for the moment.
"It's a shame because everyone thought Jacqueline could have had huge success in the role but the chance never really came off."
Jossa, who is the reigning champion of ITV's I'm A Celebrity... Get Me Out Of Here!, recently hinted that she could return to EastEnders in the near future following her successful stint in the jungle.