Toone was fit and ready to go when Skinner addressed the media at his pre-match press conference on Friday morning, but a problem cropped up the following day.
The staff are still waiting for further assessment on the injury, with uncertainty at this stage as to whether Tooney will be available for upcoming games against Everton in the League Cup in midweek, and Chelsea in the WSL next Sunday.
"It's just an injury," the boss said after beating Leicester, explaining the reason for her unexpected omission from the matchday squad.
"She had a calf issue and pulled out of training yesterday [Saturday].