Ian Evatt confirmed the former Huddersfield Town stopper, who was making his second start of the season, was withdrawn at half time because of a muscular problem.
Nathan Baxter had been included on the bench and played the second half – but he remains the only other senior option, which means the club could now look to add a new signing before the close of business on Friday.
“I thought he (Coleman) was doing really well but when he came out to gather one of the balls in the first half he felt a sharp pain in his calf,” Evatt explained.
“Obviously we are unsure how long he is going to be out at the moment but with the window still being open it gives us the opportunity to strengthen that department if we need to.”
Evatt had some better news on defender Ricardo Santos, however, with the prognosis now looking better than it did after Saturday’s 1-1 draw at Burton Albion.
It had been feared that the club captain could miss up to six weeks but the Bolton boss says he is now looking in better shape.
“It is positive and he is vastly improved since Saturday,” he added. “We are unsure about the length of time at the moment but what I will say is that it is a lot better than it was at the weekend.”