The struggling Brewers look set be without several attacking players for Saturday's home clash against Preston North End with Clough also confirming that Matty Lund and Joe Mason have been suffering with an illness.
Dyer has been out since injuring his hamstring in the 3-1 defeat to Sheffield United, while Scannell is struggling with a groin problem sustained against Sunderland in the Brewers' last home outing.
Burton midfielder Jamie Allen has also had time off due to a family bereavement.
"We've got a few doubts as always," said Clough when asked how the Burton squad looked for the visit of Alex Neil's men on Saturday.
"Lloyd Dyer has not trained yet this week, and Sean Scannell hasn't trained, so they are certainly doubts.
"We've had Matty Lund's illness - he's been off all week with one of these bugs.
"Jamie Allen is off for a couple of days with a family bereavement.
"So there are a few doubts as always going into the weekend, and we're not sure if any of them will make it.
"Joe Mason has also been ill.
"He was in the squad last week and then took ill on the Friday night and ended up in hospital.
"So we think he'll be a major doubt for Saturday as well."