Benitez has conceded that the Bundesliga team are 'of the highest level'.
"We have great respect for Dortmund," he told a Press conference. "We are talking about an opponent of the highest level.
"We're looking forward to measuring ourselves against a great squad. We need the whole team to do a great job defensively if we want to do well.
"It's a very important game for us tomorrow. We're coming up against a great side, but we have to stay calm and focused if we want to do well.
"We've played a lot of games this season at a very high level, so it's only normal that we would drop off a bit.
"But we've been training at our very best ahead of this match."
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