Agger hurt himself trying to avoid a falling weight on Sunday, as he limbered up for Liverpool's final session before they headed to South Wales.
Reds boss Brendan Rodgers revealed: "It's too early to say whether he will be fit for Saturday. He had a real freak incident in the gym. Just before he was coming out to train, he overstretched trying to prevent a dumbbell falling on his foot.
"He has overstretched and yanked his side. We are waiting to see if that settles down over the next few days. If it doesn't, we have got ample replacements. That is why we brought in extra players."
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