"I don't see anything around that would be proven at this level without paying a lot of money and if we're going to sign someone who's unproven at this level then I think our two would be a match for anybody," Southgate told the club's official website.
"We offered Mark a new contract because we felt that his experience would be a help around the place.
"But all the time we were very conscious that we have got two very good young goalkeepers who need an opportunity.
"There may be a need to take a goalkeeper just for training purposes.
"We have Jason Steele coming through as well. But I feel Brad and Ross need a chance. I will be talking to them."