Oxlade-Chamberlain sustained a knock when going in for a challenge in Austria.
Former Arsenal midfielder Oxlade-Chamberlain will miss the rest of Liverpool's pre-season tour.
Liverpool boss Jurgen Klopp has confirmed Alex Oxlade-Chamberlain will miss the start of the 2020-21 season.
The England international suffered a knee injury in Liverpool's pre-season training session in Austria ahead of their Community Shield clash against the Gunners next weekend.
The Mirror confirmed Oxlade-Chamberlain, 27, has already flown home to Melwood to begin his rehabilitation and will miss Liverpool's friendly matches against Stuttgart on Saturday and RB Salzburg next Wednesday.
Chamberlain will also miss Liverpool's Community Shield clash against his former side Arsenal the following Saturday.
Klopp told the media: "Really unfortunate. An unfortunate situation as well; it was a challenge [in training].
"It looks like it is very similar to what Hendo had, which keeps him out for we don't know for sure exactly how long, but for sure this pre-season he will not make a game, Arsenal for sure not and then we will see. The next game is probably two weeks later, but I don't know.
"We have to wait but it is far away from being perfect, of course. It is really hard for him and hard for us, but it is not to change."