The centre-back lasted just 18 minutes of the game in North Carolina before suffering a muscle injury, though manager Jurgen Klopp insisted that it was not the same problem that ended his campaign prematurely in April.
"It's not the same injury. It's another muscle - it looks like, hopefully, only a little tear," Klopp told Liverpool's official website.
"We will see, but we cannot say any more about it now. It is, of course, the most negative thing about the day. It's not cool. Things like this can happen, but you don't want them to.
"Maybe tomorrow or the day after tomorrow we will know more, but in this moment we only know that it was too painful for him to carry on."
Matip hasn't played for Liverpool since March and his niggle will be a major concern if he is not back fit for the start of the Premier League season, with Dejan Lovren having been handed an extended break due to his World Cup involvement.