The England international made a tackle on Aleksandar Kolarov and injured himself in the process:
Oxlade-Chamberlain has enjoyed a breakout season in 2017-18, his first with the Reds after a lengthy spell with Arsenal. He established himself as a top prospect with the Gunners but failed to take the next step in his development, leading to the move to Anfield.
Under manager Jurgen Klopp, the 24-year-old made a slow start, but he's become more important to the side as the season has progressed. Seeing him start in a crucial semi-final was no surprise.
It would be a cruel blow for the technician if the injury turns out to be a serious one, as he could miss out on the rest of the Champions League run and the upcoming 2018 FIFA World Cup in Russia this summer.
According to Klopp, the injury is a bad one, as shared by ESPN FC's Mattias Karen:
The Reds have a capable replacement in Georginio Wijnaldum, but they would much rather face Roma―and a potential trip to the Champions League final―at full strength.