Arne Slot says Liverpool are waiting to discover the extent of Curtis Jones' injury, after the midfielder was forced off during the Reds' 1-0 victory over Real Betis.
The Dutchman oversaw his first win since replacing Jurgen Klopp at Anfield, with Dominik Szoboszlai scoring the only goal in Pittsburgh.
It was the first match of the Reds' pre-season tour of the United States, though it remains to be seen how much of a part Jones will play after he limped off on the half-hour mark.
However, Slot said the decision to withdraw the midfielder was precautionary.
"I think it's too early to tell [how bad it is]," he told reporters during his post-match press conference. "Maybe he could have played on, but I think maybe you could see he was not at 100%.
"In a friendly game, with so many days coming up in our tour, it was best to take him off. We hope he recovers really fast, so we can see him in the next few games.
"It's always a pity if he has to go off after 25 minutes, half an hour. And before that, you could see that he was not completely free.
"It was unfortunate because he had two really good weeks during the training sessions, so I looked forward to seeing him in the game, but unfortunately he had to go off.
Trey Nyoni replaced Jones for the remainder of the game, and Slot was pleased by the 17-year-old's impact.
"The good thing about that was that we brought someone [on] that impressed me in the 45 minutes to an hour he played afterwards.
"I think [Trey] did really well today, but it was only an hour. He was one of the reasons why we scored the goal, because he turned really quickly and [played] a spot-on pass in between the lines. And he was also involved in the biggest chance in the second half.
"We are really careful with him. So he doesn't join every session, and sometimes he goes off a bit earlier. You can see his quality, but you can also see his body still needs some time to grow to play at Premier League level. But he showed some interesting things today.
I think there were a few positive things and, of course, a few things we have to improve. But the positive thing is that we kept a clean sheet. I think we only conceded one big chance and that was somewhere around the last 10 minutes of the game.
"So, we controlled the game really well and, in between, we had a few good attacks where we created a few good chances and scored a good goal."