Liverpool have announced that Adam Lallana will miss "a couple of months" of action with a thigh injury.
Lallana suffered the injury in the final of the Audi Cup while playing Atletico Madrid on Wednesday in Munich.
Klopp was brought in as Liverpool's new manager back in October 2015 following the sacking of Brendan Rodgers.
Last season saw Liverpool finish in the Premier League's top four for only the second time in eight seasons.
The loss of the 29-year-old leaves Klopp somewhat light in central midfield, with Jordan Henderson, Emre Can and Georginio Wijnaldum as recognised options in the position. Actually, it was exactly what I expected when I had a look - if there's a choice we always seem to take the German team. "It's Hoffenheim and that's for sure not an easy game", said Klopp.
Navy ends search for sailor lost in South China Sea, officials say
Hopkins was reported missing about 9 a.m.as the ship transited 140 miles west of Subic Bay, Philippines, a Navy statement said. The Chinese navy and two Japanese military ships aided in the search.
Klopp was also without his trusted assistants, Zeljko Buvac and Peter Krawietz, who were in Germany to scout Hoffenhiem ahead of the first leg on August 15.
"They have a lot of really good young players".
In the Champions section of the draw, Scottish club Celtic were drawn against Kazakh side Astana.
"Hoffenheim will present a tough passage for Pool but they have lost key personnel during the summer and once again we make Liverpool strong favourites at 1/3 to qualify and 9/4 to be eliminated".
In addition to the growing injury concerns, the Merseyside club were dealt a tough tie in the Champions League qualifying round against Bundesliga dark horses Hoffenheim on Friday.