The England international picked up the injury to his thigh during the first half of the Audi Cup final against Atletico Madrid in Munich on Wednesday with the full extent of the problem only determined when Liverpool returned home on Thursday after their training camp in Germany.
It’s a big blow to Liverpool as Lallana established himself as a key player in a new midfield role last season, and Klopp will now be forced to plan without him for the start of the campaign.
Midfield is not an area that Liverpool are particularly deep at the moment after falling to sign Naby Keita from RB Leipzig this summer and with continued speculation of the future of Philippe Coutinho following Neymar’s move to Paris Saint-Germain.
‘This is certainly not news we would have wanted” said Klopp.
‘Unfortunately, the damage is such that it will likely mean Adam is out for a couple of months not weeks, so I think we can pretty much rule him out of August and September.
‘Beyond that we will monitor and wait and see. He is a boy with a world-class attitude to everything professionally and he has always come back in good time from injury setbacks since I have been here, so we will see.’
Lallana missed a significant chunk of the run-in last season after being injured playing for England against Lithuania in March but he returned in time to feature and score on the final day as Middlesbrough were beaten 3-0 to secure fourth place.
There is no indication yet when Lallana will return but there is no question that his absence will be keenly felt; Liverpool face Athletic Bilbao in Dublin today and their squad will not include Daniel Sturridge, who injured his thigh against Bayern Munich 24 hours earlier.
Lallana will now join Daniel Sturridge, Nathaniel Clyne, James Milner, Dejan Lovren and Joe Gomez on the sidelines ahead of Liverpool’s trip to Watford net week.