Andy Robertson will undergo a scan after suffering an ankle injury in Liverpool's friendly against Athletic Bilbao on Sunday.
The Scotland international twisted his ankle during the 1-1 draw at Anfield, less than a week before Liverpool begin their Premier League season at Norwich next Saturday.
Liverpool manager Jurgen Klopp must now wait to learn the severity of the injury to Robertson, who did not miss a single league match in the previous campaign.
"We obviously don't know in the moment how serious it is. It was pretty painful and that's why Andy went off," Klopp said.
"You probably saw it on the TV pictures better than we did, but he got the ball, the ball on the front of his foot, [and] twisted the ankle.
"The pain settled already, but we cannot say anything further without further assessment tomorrow. He has to get a scan and then we will know more."
Diogo Jota was on target as Liverpool drew their penultimate pre-season friendly, producing a fine finish in the box on 13 minutes to get the Reds up and running.
Alex Berenguer equalized for Athletic Bilbao on 53 minutes and while Liverpool were not as dominant after the break, they hit the woodwork when the impressive Harvey Elliott bent a left-foot shot against the far post, and looked in good shape ahead of their Premier League opener at Norwich next Saturday.