Rotherham boss Steve Evans revealed Wes Thomas suffered a groin injury in Saturday's 2-1 win over Leyton Orient.
Thomas opened his Millers account by giving his side the lead with a deft header in the first half but was withdrawn at the break and replaced by Tom Hitchcock.
Evans confirmed the injury is not serious and the decision to remove him was a precaution.
"He was just feeling his groin," the manager said. "We couldn't take the chance, he wanted to play on but I made the decision, we don't want to lose him for weeks, we wanted to be precautionary.
"I took the decision away from him because he wanted to go back out."
The Millers were also without midfielder Rob Milsom who had a thigh injury, though that problem is not serious either.
"It's not a severe issue, he had a little thigh injury in midweek and we knew he wouldn't be 100 per cent," Evans added. "It was a big decision who we went for between Richie (Smallwood) and Michael O'Connor but we got a call from Michael who had a blow out with his tyre and didn't know if he'd make it on time so that enforced the decision."
Meanwhile, Evans has received some positive news with the return to first-team training of skipper Craig Morgan.
The centre-half has been out of action following surgery on a floating bone in his foot, but is back in full training and should lead the team out at Colchester on Saturday.
"We're looking forward to getting our captain back on the teamsheet, he is a player we have missed over the last few weeks," Evans said.