"It's massive. If you talk about the top end of the Premier League and the top end of the Championship it's massive," he said.
"The technical ability, the power there - it's kind of the arrogance as well.
"If you play for a top-level side, they all seem to come on the pitch with a kind of arrogant swagger where they know they're not going to get beat."
Bent admits Derby struggled to cope with Liverpool's high intensity on the night.
"What really impressed me last night what how hard they work," he said.
"Even though they had the ball a lot of the time, every time we got the ball and tried to keep it they were after us.
"They tried to win it back within five to ten seconds - they made it really difficult for us to get anything going really.
"We played as well as we could and gave it a good go but in the end it just wasn't good enough.
"They kept possession so well, moved the ball, looked dangerous, effective and I'm sure they're going to have a good season this year."