The Reds are set to face the Portuguese outfit in the second leg of their quarter-final clash.
Liverpool have a 3-1 lead from the away leg, and will be looking to finish off the tie at home on Wednesday.
"Nobody is injured but we need to look who is fresher for the game and stuff like this," said Klopp.
"The next game [FA Cup semi-final vs. Manchester City] has no influence on the line-up for tomorrow but the last game has."
"We tried so hard to get to the Champions League and now we can make it to semis," he added.
"It's 3-1 at half-time, it's as tricky as 2-0. A good basis, but if they score one - like we felt against Inter - the game changes.
"We felt it when they scored last week. We really need to make them feel this is a place they don't want to go."
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