Liverpool midfielder Naby Keita has been ruled out for at least two months with a groin injury which will mean he misses the African Nations Cup.
The Guinea international limped off midway through the first half of the 3-0 Champions League semi-final first leg defeat to Barcelona in the Nou Camp on Wednesday.
He is now likely to be sidelined until the squad return for pre-season training in July.
"It was really unlucky. Bad news, a high-grade adductor injury with the tendon rupture so it keeps him out for at least two months," said Klopp, who will be without the midfielder for Saturday's trip to Newcastle, as well as home games against Barcelona and Wolves on the final day of the campaign.
"Bad news for us and for Guinea with the Africa Cup of Nations coming up. Not nice.
"Very serious. For sure he is not in the best moment. African Cup of Nations was a big target for him."
