The Pole had a problem with his toes in training and felt unable to kick the ball properly as he prepared to play in yesterday's victory over Aberdeen.
"When he (Boruc) warmed up he felt he couldn't perform so we had to change it," Strachan said. "Brown didn't have much to do but I felt he was all right. His kicking was good, he was confident when the ball was rolled back to him so we were pleased with that."
When asked if the Pole would be back for the visit of the Ukrainians, Strachan said: "If he is there a minute before kick-off and decides he is all right then he will be fine.
"There is something wrong with his toes, he can't kick the ball properly.
"He has picked up something, a fungal infection or something like that."