No wonder: his father remains kidnapped by Colombian rebels.
Yet despite the personal anguish, he not only requested to be in Juergen Klopp's squad for the game, but then came on and scored a last-ditch equaliser.
Not surprisingly, there was no whirling away in delight this time. Rather, Diaz lifted up his shirt to revel a white undertop with words in black: "Libertad Para Papa" (Freedom For Dad).
Though his goal - off the shoulder after a great leap - had broken Luton fans' hearts, they too joined Liverpool supporters in a wave of applause for Diaz as he left the pitch.
"We're supporting him and feeling his pain - but for him it's a different level," said Liverpool goalkeeper Alisson (31).
Colombia's National Liberation Army (ELN) guerrillas have said they will release Luis Manuel Diaz, as they did Diaz's mother. That cannot come soon enough for player and club.
"A wonderful moment. But it doesn't change the situation. The most important thing is that his father gets released," Klopp said of the goal in the fifth minute of added time.
"We knew he would be a threat. We didn't know how long he would play because he only had a few sessions with the team.
But that is not the most important part today. He scored the goal but we need to see some improvement in Colombia."