Ferguson saw both John O'Shea and his replacement Rafael go off with suspected hamstring injuries which could prove problematic as the United squad chase success on three fronts.
The injuries forced Ferguson to make substitutions he felt unsettled his team and contributed to an anxious end to the game.
"It was nervy because so many players came off with injuries,'' he said.
"It shifted the balance of team. I would have rather brought on Darron Gibson because the problem tonight was always going to be height and it caused us problems.''