Delaney travelled to Sweden as part of the Villa squad, despite missing a previous pre-season friendly at Wycombe, however, will now return home as the problem continues to trouble him.
O'Leary said: "Hopefully there won't be anything.
"But he can't train here and the medical department want to let the club doctor have a look at him."
"So he'll have the scan back in England some time later on Friday and then from there we'll know the full extent of the injury."