McDonald was ruled out of Saturday's 3-1 defeat at Bolton after suffering an injury in training.
Lomas will also have defender Mark Beevers, who was an unused sub at the Reebok Stadiium after six weeks out with a knee injury, fully fit in a fortnight.
"Scott tweaked his hamstring in training on Thursday but we're hopeful that it isn't a bad one," said Lomas.
"We have the international break now and that allows players like Mark Beevers that extra time be ready to fight for a place for the Barnsley game."
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