The ex-Norwegian left-back feels that the Reds are missing something.
The Reds sit seventh in the Premier League table, six points behind fourth-placed Manchester City in the race for Champions League qualification in what has proven a lukewarm start for Klopp, who replaced Brendan Rodgers in October.
The likes of Brazilian duo Roberto Firmino and Philippe Coutinho seem especially impressive under the ex-Borussia Dortmund coach, but having played alongside Steven Gerrard, Sami Hyypia and Jamie Carragher during his trophy-laden stint at Anfield, Riise believes that flair will only get a team so far.
“The fans love to see aggression and passion. When I played for Liverpool, no team liked to come to Anfield and face us because they knew they would be in for a tough game, where there would be plenty of aggression and attack," he told Four Four Two.
“That level of intensity and passion is coming back and it comes from the influence of the manager, but Liverpool also need to bring in new players.
“Yes, you need the creative players like Firmino and Coutinho, but you also need people to get stuck in and smash the opponents like how Didi (Dietmar Hamann), Jamie, Hyppia, Steven, and (Javier) Mascherano did when I was there.”
Klopp's side demonstrated how good of an attacking force they can be by thumping Man City 3-0 at Anfield last week, though the fact they are so far adrift of leaders Leicester City - 16 points - may be a worry.
Still, the 48-year-old will not be judged until he has had a chance to put his own stamp on the side by presiding over a summer transfer window.