The Arsenal loanee suffered a thigh injury while away on international duty with England U20s.
He returned to Rovers on Thursday but did not take part in training as Rovers wait for a scan to be able to fully diagnose the issue.
“He’s okay but we’re just waiting back on one of the scan results to come through from the FA before determining it and knowing what we’re dealing with,” boss Darre Moore said.
“We’re a little bit still in the dark.
“He seems okay and he’s in good spirits.”
Moore was non-committal on John-Jules’ potential involvement on Saturday but feels the striker would be ready if given the green light.
“Because we’re waiting for the results, they can show things that determine your decision”, he said.
“You don’t want to go into the game in the dark with it, which is where we are at the moment.
“We’ve got a cluster of fixtures coming up now and we’ve got to be ready for it.
“England didn’t play him because with it being a friendly there was no need to risk him, which we’re grateful for.
“We had him with us but he didn’t train just in case.
“Because he’s been training with the international group, he’s not missed much. He’s just missed a couple of days.”
John-Jules sat out England U20s friendly with Wales U19s on Tuesday due to his injury.