Hannover 96 midfielder Leon Andreasen will be out for roughly six months after his encouraging comeback from a long layoff was curtailed by torn cruciate ligaments suffered in the midweek 4-1 win over Nuremberg, the club said.
The Danish international, who had recently returned from a two-year injury absence, had scored two goals in five league games and another three in the Europa League.
"I suspected something was wrong when it happened. It hurt a lot and the diagnosis is no real surprise," Andreasen told the club website of the injury to his right knee.
"This is a bitter blow, but I have to look ahead and I am sure can come back again," the former Fulham player said. Hannover, third in the Bundesliga, travel to Hamburg SV on Saturday.
Reus, who joined for 17 million euros in the off-season, twisted his ankle during Wednesday's 3-3 draw at Eintracht Frankfurt and looked set to miss Saturday's encounter.
"I will wait and see how his foot holds up in full training on Friday before deciding," Klopp said.
