Wanderers are waiting on the results on further scans to determine how long Gethin Jones will be out of action.
The Welshman has missed the Whites’ last three matches after suffering a stress fracture in his fibula in training.
Last week, Ian Evatt revealed an initial scan suggested John could be ruled out until January but added that the club were seeking a second opinion.
Speaking ahead of his side’s trip to Portsmouth over the weekend, the Bolton boss said there had been some positive early signs in the defender’s recovery.
“The good thing is he’s out of his boot, he’s pretty much pain free,” Evatt told The Bolton News.
“It’s just to the extend of how that bone has now healed. It’s not a weight-bearing bone which is important.
"Your fibula is a bone that we all have but it’s not necessarily weight-bearing, even though it can cause you some discomfort, so we’re more hopeful than anything else that it will be quicker than the initial diagnosis.
“But at the moment we’re just waiting to hear what happens today (Thursday).”
Wanderers forward Amadou Bakayoko is also ruled out of Saturday’s trip to Fratton Park after suffering an ankle injury against Gillingham.
Eoin Doyle is also a doubt due to illness but George Johnston is available after being forced off at half-time with a knee problem.