Ireland pin hopes on O'Sullivan recovery after injury in abandoned friendly
A scan on O'Sullivan's shin revealed no fracture, but she returned to the team hotel wearing a protective boot and using crutches following a game in which her coach Vera Pauw (60) said the Irish players feared for their physical safety.
"There was potential for a big injury (to O'Sullivan), the doctor feared that last night, but that the X-ray showed there is a chance she makes it," Ireland coach Pauw told state broadcaster RTE.
"It is a serious injury. The first 48 hours are very important, she is off her feet, (but) we have good hopes."
Alongside captain Katie McCabe (27), O'Sullivan is one of Ireland's most important players, and it was her pinpoint pass that set up striker Amber Barrett (27) for the goal against Scotland that ensured their qualification.
Friday's game against Colombia was supposed to be an opportunity to give all her players a run before the tournament, but Pauw decided to end the game because of what she deemed to be reckless play by the Colombians.
"At first, there was a huge challenge on Ruesha (Littlejohn)," she told reporters. "We ourselves as a team play within the rules of the game, (we're) a very tough-playing team. This was out of the rules of the game."
The challenge on O'Sullivan resulted in the game's second yellow card, and Pauw said she consulted with both the Colombian coaching staff and officials at the Football Association Of Ireland (FAI) before withdrawing her players from the field.
While the loss of O'Sullivan would be a huge blow, Dutch-born Pauw said her side had prepared for every eventuality.
"We played against Zambia without Denise and we won 3-2... we have a squad who have a knowledge of their tasks and the execution of those tasks," she said.
"Every single scenario has been discussed over this period... and this is one of them: what do we do if she is injured? So those scenarios are ready, for every single player. They were ready before this."
Playing at their first major finals, Ireland face Australia in a sold-out tournament opener on Thursday. They take on Olympic champions Canada in Perth on July 26 before rounding off Group B against Nigeria in Brisbane.