Gary Kelly is to see a specialist today after breaking down at Elland Road yesterday.
Kelly, who had operations on both his shins in October, was warming up before Leeds United's reserve team game against Everton when he said his legs "just gave out".
"There was no indication of trouble when I went on the pitch to warm up, but when I tried to run, I couldn't do it. I am very disappointed," he said. "I had already played two half games for the reserves against Birmingham and Sunderland, but now I'm back to square one. I'm told that it could be a problem with circulation, but at this point the calves of my legs are very sore."
The news of the setback will disappoint Mick McCarthy who had expressed satisfaction that the Leeds player was making good progress when he announced his Irish squad on Monday.