The 20-year-old right back will miss the Champions League quarter-final first leg against Manchester City at Anfield next week.
"It's serious enough to leave him out for a couple of games but not until the rest of the season," Klopp told reporters on Friday.
"It's difficult to give a time schedule but we hope that he's back in training in three to four weeks."
Can pulled out of the Germany squad for friendlies against Spain and Brazil as he recovers from the back injury he suffered in Liverpool's 5-0 league win over Watford this month.
Defender Nathaniel Clyne is fit again after back surgery and could make his first appearance of the season against Roy Hodgson's side.
Klopp does not expect an easy match against 16th-placed Palace, who are two points above the relegation zone.
"It will be difficult for sure... they fight (to stay in) the league and we fight for the Champions League," the German said.
"They've had key players out - if they had constantly been together on the pitch they would be in another position in the table... they're not a typical team. They're in good shape. Roy is doing a fantastic job."
A win would improve Liverpool's chances of finishing in the top four as they look to qualify for next season's Champions League. They are third in the table with 63 points.
(Reporting by Shrivathsa Sridhar in Bengaluru, editing by Ed Osmond)
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