LONDON (Reuters) - Liverpool have been roughing up Loris Karius with rugby tackle pads in training to help the goalkeeper adapt to the physicality of the Premier League, manager Jurgen Klopp has said.

The 23-year-old Karius, who joined from German side Mainz 05 during the close season, has usurped Simon Mignolet in the starting line-up but is yet to win over the Liverpool faithful following a string of erratic performances.

Goalkeeping coach John Achterberg has been pictured at the club's training ground challenging Karius for high balls while holding a rugby tackle bag.

"John Achterberg usually does it with his hands but it's better to use something else," Klopp told British media. "Of course that's important. There are different things you have to do as a coach

"First, as a keeper you have to learn the technique then you have to adapt to the real circumstances - having six, seven players around you.

"No-one gets out of your way. It is completely the opposite. They want to disturb your way.

"It was specific training for goalkeepers in the Premier League. That's goalkeeping life. You can't change this ... so we need to prepare the boys and that's what John is doing."

Liverpool have been in fine form this season and sit third in the Premier League, behind leaders Manchester City only on goal difference.

The Merseyside club host seventh-placed Watford on Sunday.