Kewell, speaking to the club's official website, said: "He has really been putting us through our paces and the muscles are aching, but this is an important time of the season because we're all looking to make a good impression.
"There's definitely a new buzz around the place. When new people arrive it means it's a new start for everyone and we all start from scratch. It's still very early days but so far I'm really enjoying it."
Liverpool's mediocre form in the past season was mirrored by that of Kewell, who struggled to find his feet following his controversial move from Leeds, but the 25-year-old has vowed to show his true potential in the forthcoming campaign.
Kewell added: "I've said before that I wasn't happy with my form towards the end of last season. Most people will probably say I did ok, but for me just doing ok isn't enough. I always want to do better.