Mohamed Salah has posted a message of support to his Liverpool team-mate Loris Karius on social media, urging the goalkeeper to "ignore those who hate".
The Reds' 3-1 friendly loss to Borussia Dortmund in Charlotte on Sunday saw the Bundesliga side score their final goal when Karius could only parry a Christian Pulisic shot before Jacob Bruun Larsen tapped in.
Karius was at fault for two of Real Madrid's goals when Liverpool were beaten 3-1 in May's Champions League final, after which it was revealed the 25-year-old German was suffering from concussion.
He also spilled a free-kick, allowing the hosts to score, in Liverpool's friendly against Tranmere at Prenton Park earlier this month.
Following the game against Dortmund, forward Salah wrote on Twitter: "Stay strong Karius, it has happened to the best of players. Ignore those who hate."
Karius himself had posted a message via an Instagram story after the match which read: "To those who take joy in seeing other people fail or suffer, I feel for you.
"Whatever it is that's happening in your life to hold this much anger and hate, I pray that it passes and good things come to you."
Liverpool last week paid the highest fee for a goalkeeper in history to sign Alisson from Roma in a deal worth up to £65million.
Karius was quoted by the Liverpool Echo as telling Sky in Germany after the Dortmund match: "Of course that's not perfect for me, but I cannot say much more about that.
"I do not know that (whether he will leave before the transfer deadline). I cannot say what I'm doing right now, there's still some time left."
Early on in the contest in North Carolina, Liverpool's Joel Matip was forced off with an injury.
The defender, whose 2017-18 season was cut short by a thigh injury which required surgery, limped off 22 minutes into the International Champions Cup clash at Bank of America Stadium.
Liverpool boss Jurgen Klopp played down concerns the issue was a recurrence of the previous problem, saying it was a "little tear", and the player would be monitored over the next few days.
"It's not the same injury. It's another muscle - it looks like, hopefully, only a little tear," Klopp said at his post-match press conference, quoted on the club's 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 on Tuesday we will know more, but in this moment we only know that it was too painful for him to carry on."
Matip's last appearance of 2017-18 came in March, with the Cameroon centre-back sustaining a thigh injury against Crystal Palace and subsequently going under the knife. He made his return to action in Liverpool's friendly against Bury on July 14 and then played in a game at Blackburn.
Liverpool took the lead against Dortmund three minutes after Matip was replaced by Joe Gomez, Virgil van Dijk producing a fine header.
Dortmund levelled in the 66th minute as Pulisic converted a penalty after being fouled by James Milner. Nineteen-year-old American Pulisic then fired in from the edge of the box in the 89th minute, before Bruun Larsen added a close-range finish.