Callum Brittian is set for a couple of weeks on the sidelines with an ankle injury sustained in training.
The defender missed Monday night's 4-1 win over Wrexham after he rolled his ankle on Thursday. Brittain went for a scan and now looks set for a few weeks out.
Harry Leonard was also unavailable due to illness. That meant Niall Ennis was on the bench again, though an unused substitute. He could still leave the club before the January window shuts.
"Harry is ill, Callum has an ankle problem," Tomasson said.
READ MORE: Adam Wharton edging closer to Crystal Palace move
"It's disappointing because it's one of the positions we are extremely stretched. Hopefully, we can get players in to strengthen the squad generally.
"I hope it'll be less than a month but he won't be playing tomorrow. I don't know if it'll be two, three or four weeks but he won't be back tomorrow. I don't expect him to be out for a month."
Losing Brittain further depletes Jon Dahl Tomasson's options at the back with Hayden Carter and Harry Pickering sustaining long-term hamstring injuries last week.
Joe Rankin-Costello played as an emergency right-sided defender against Wrexham, though Connor O'Riordan will be available to face Queens Park Rangers after being cup-tied.
Rovers also expect to sign an experienced centre-back in the final days of the January transfer window.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereLast Updated:
Report this comment Cancel