Tony Mowbray has admitted he will have to venture into the loan market to find a replacement for Jason Steele.
Steele picked up an injury during the 5-2 defeat to Reading on Saturday and could be facing a spell on the sidelines.
Middlesbrough have no other senior goalkeeping options with Danny Coyne still two weeks away from a return to action as he recovers from hernia surgery and a back problem.
Connor Ripley, 18, came on to make his debut in place of Steele at the weekend but was then allowed to play in the FA Youth Cup game against Aston Villa on Sunday, indicating that he will not be considered for Boro's crucial Championship game against Derby on Tuesday.
Mowbray therefore recognises that he will need to secure an emergency loan deal as quickly as possible.
Pain and discomfort
"We'll have to assess Jason's injury but it's probably a muscle tear in his side," the Boro boss told his club's official website.
"He's in a lot of pain and discomfort.
"We haven't got another goalkeeper at the club other than schoolboys so we're going to have to do that (look for somebody on loan).
"We'll address that as quickly as we can."