The Baggies slumped out of the competition in a 1-0 loss to QPR in their third-round replay at The Hawthorns last night but Clarke has defended his decision to tinker with his team.
"I only made four changes and two of them were enforced," the Express & Star quotes Clarke as saying. "I couldn't risk Jonas Olsson after he'd been out for so long by playing him in two games in such a short space of time.
"We have other important games coming up. And Chris Brunt has the flu. The squad has really been stretched to the limit over the last six weeks and we are not quite getting the breaks we need, at the moment."
Meanwhile, the Baggies switch their attention to the Premier League this weekend when they host Aston Villa.