Before taking charge as the manager of Liverpool in 2015, Klopp served as the coach of Bundesliga club Borussia Dortmund for seven years between 2008 and 2015.
The German tactician enjoyed significant success during his time at Signal Iduna Park, helping Dortmund win the league title twice and win three domestic cups.
While the Black and Yellows have had five different coaches since Klopp’s departure and are now set to appoint Marco Rose, none of them has been able to replicate the Liverpool boss’ success yet.
Frei, who played for Dortmund between 2006 and 2009, is of the view that all coaches that arrive at Signal Iduna Park are compared to Klopp and believes it is unfair toward the tacticians.
“In the end, Borussia Dortmund will end up in third or fourth place because the quality of the squad is simply too good to not make it into the Champions League“, Frei told German magazine Sport Bild.
“The problem with Borussia Dortmund is that all coaches are measured against Jurgen Klopp.
“And that’s not fair.
“When I came to Dortmund in 2006, I immediately felt that this club were sleeping giants.
“Kloppo had exactly the right feeling for how to wake this giant.“
After leaving Dortmund, Klopp led Liverpool to their first Premier League title in 30 years and their sixth Champions League trophy.