ROTTACH-EGERN, Germany -- Ragnar Klavan says Peter Crouch was one of most difficult strikers he faced in his first season in the Premier League.
Klavan joined Liverpool last summer from Augsburg for £4.2 million and made 25 appearances last term as backup at centre-back.
The 31-year-old faced Sergio Aguero, Romelu Lukaku, Harry Kane and Zlatan Ibrahimovic throughout 2016-17, but feels the Stoke City striker, who played for Liverpool between 2005 and 2008, gave him the most challenging encounter.
When asked at Liverpool's base for their German training camp who was his toughest opponent, Klavan replied: "I'd say that the biggest surprise was Peter Crouch. Really!
"He was good. He was fast enough, he was strong enough and he was technical enough. I had never played against him before. When I came up against him it was a positive surprise."
Klavan added: "[My first season] was harder than I thought. It took a while to get used to it -- learning what's allowed in that league and what's not.
"I think it was alright. I tried to help the team as much as possible. I had some good games and some not so good games. It was like that for the whole team -- up and down.
"It's hard to say how this season will pan out but there will be more games this season with Europe compared to last season.
"I don't know how the manager will solve that problem. When he needs me, I'll be there."
During preseason, manager Jurgen Klopp has repeatedly talked about improving Liverpool's defence, which conceded 42 goals in the league last season -- the most of any team in the top four.
Klavan says defending in a Klopp side is "different" and requires greater concentration because of the Reds' front-foot attitude.
"It's a bit in your head," the Estonia international continued. "With the football we play, most of the time we are the attacking side. You want to bring more energy and focus on the attacking side.
"When it suddenly changes then maybe we aren't quick enough in our heads to make that change and protect our goal. That's one of the points we are working on to make that change a bit quicker.
"It is different for sure. You are involved in every aspect of the game. You always have to be in the game so it's a big change."