The on-loan Wolverhampton Wanderers striker sat out the stalemate at the Keepmoat after picking up what Darren Moore labelled ‘a slight strain.’
And the Rovers boss admits it will be touch-and-go whether Ennis is fit for the weekend trip to Kingsmeadow.
“It was nothing major but Niall suffered a slight strain,” Moore said.
“It’s one of those decisions, with us signing Rakish as well, it made it a little easier for me to leave him out.
“Niall wouldn’t have been fit so with Rakish coming in it was one body out and another in. We were able to replace him.
“We’ll wait and see how the week pans out.
“I’m the sort of manager where if there's any doubt then I'd rather leave them out because I look to the longer term.”
Midfielder Ben Sheaf was withdrawn at half time on Saturday with Moore revealing he took a risk with the Arsenal loanee having been ill in the build-up to the game.
“He was ill before the game and we took the chance”, Moore said.
“Sometimes you can have these illnesses and your adrenaline takes over when you get out there.
“Ben wasn’t fully up to speed so we took the decision to take him off at half time and put Madger [Gomes] on.
“Hopefully he’ll recover over the next couple of days.
"It’s that time of the year where cold and coughs and sniffles are around and I’m sure the next couple of days will do him the world of good to get him back up to speed.”
Ben Whiteman hobbled off the pitch at the end of the game but Moore expects him to be fine.