The 17-year-old winger had been one of Liverpool’s brightest performers, setting up Ryan Gravenberch’s opener and continuing his breakout campaign with another influential display.
Ngumoha’s assist took him to three goal contributions this season and underlined why supporters have quickly taken to the academy graduate.
So when his number went up in the 67th minute, the reaction was immediate.
“No, I wasn’t surprised,” he told TalkSPORT.
“I knew the moment his number went up that that would have been the reaction.”
Slot said he understood the frustration, but insisted the substitution was driven purely by fitness concerns.
“I would have loved to see him play 20 or 25 minutes more.”
“But the reality is that three minutes before that, he went to the floor with cramp attacks.”
“I asked him how he was, and he said to me that I had to take him off.”
Ngumoha, formerly of Chelsea’s academy, became one of the youngest players ever to score or assist in the Premier League against his former club.
The teenager’s rise has become one of Liverpool’s brightest stories in a season filled with scrutiny.
Slot may have silenced the questions.
But the reaction inside Anfield showed just how quickly Ngumoha has become a player supporters do not want to see leaving the pitch.