"This is certainly not news we would have wanted, but we have no choice".
He added: "We've had a lot of games in pre-season and we didn't lose one".
"That's more or less a waste of time!".
Liverpool play Arsenal the following weekend.
Liverpool must come through a tough two-legged play-off tie against Hoffenheim if they are to return to the group stage of Europe's premier competition after missing out for three season. Then we have to see how this works. The news of Lallana's injury has been compounded by Barcelona target Philippe Coutinho, who has been ruled out of the Reds' final pre-season friendly with Athletic Club after suffering a minor back problem. The versatile player is set to miss "a couple of months", as per Klopp's official confirmation.
Klopp changed all of his outfield players at the half-time break and two of the youngsters introduced went on to play a starring role. We still have to have a style, a way of playing and we need to be able to play completely differently if needed. We've got people getting you 10 or 15 but if you can get someone who can get you 25 goals a season, that could be a big, big difference.
The Glasgow club will host Astana in the first leg before a journey of almost 4,000 miles for the return leg on August 22 or 23.
Whatever moves take place, it seems Klopp is quite satisfied already.
The Reds are still waiting to win their first piece of silverware under Jurgen Klopp after the former Borussia Dortmund coach was appointed as Brendan Rodgers' successor in October 2015.