Brentford have completed the signing of former Barnet goalkeeper Liam O'Brien on a short-term deal.
The 21-year-old was released by the non-league side earlier this summer.
"The risk is too high to have only two fit goalkeepers as Richard is not able take part in full training at the moment," Bees boss Uwe Rosler said.
"It will take a few weeks more and we want to be covered in all areas.
"We will see how the situation develops."