Slot made ten changes to the side that lost 3-2 at Brentford, keeping only Milos Kerkez in the starting XI. The Dutchman opted for a youthful squad dominated by academy talents, with just one senior outfield player among the substitutes, giving starts to youngsters Calvin Ramsay, Trey Nyoni and debutant Kieran Morrison, alongside experienced figures such as Federico Chiesa, Joe Gomez, Andy Robertson, Wataru Endo and Alexis Mac Allister.
The result marked Liverpool's sixth defeat in seven matches, with the pressure beginning to mount on Slot ahead of Saturday's Premier League clash with Aston Villa. Palace's win earned them a quarter-final meeting with league leaders Arsenal.
"It's not of Liverpool's standards to lose five out of six, to lose six out of seven," Slot said. "The pressure might increase a little bit but not so much because the pressure was already high, again we have to face three very difficult teams (in the next week)."
He defended the approach by pointing to the schedule and squad constraints, adding: "We played three matches in seven days, including a trip to Frankfurt, and some of our players are still adjusting physically. I didn't want to risk more injuries.
"At this time we have only 15 or 16 (senior) players available and this club always used this competition for their academy players. This felt the right decision and I haven't changed my opinion after the result."
Slot referenced previous experiences with player injuries, noting the need to avoid repeats after recent setbacks. He also drew comparisons with Manchester City's depth, saying: "If you look at City's line-up, it looks like they have 11 starters, even when they rotate. That shows the size of their squad. We are missing only four players, but that means I still had to include four under-19s."
Liverpool's night worsened when substitute Amara Nallo was sent off in the 79th minute, just 12 minutes after coming on, receiving a straight red card for bringing down Justin Devenny as the Palace player broke clear on goal.
Slot revealed that senior defenders Virgil van Dijk and Ibrahima Konate consoled the young centre-back after full-time. "I didn't need to say much," Slot said. "Ibou and Virgil immediately went to speak with him. That shows the kind of people they are, they understand how hard that moment was for him."
Liverpool now turn their attention to Villa, as Slot looks to stabilise a squad hit by fatigue, injuries and a growing sense of frustration.
Nottingham Forest manager Sean Dyche has confirmed that striker Chris Wood will miss Saturday's Premier League clash with Manchester United as the club's injury list continues to grow.
Manchester United have been handed a major boost ahead of their clash with Nottingham Forest, as Lisandro Martinez has returned to full training following a long injury .
Burnley are hosting top of the table Arsenal in their Premier League encounter at Turf Moor on Saturday as they look to extend the two-match winning run.
Manchester City are grappling with ongoing injury worries ahead of Sunday's Premier League encounter with in-form Bournemouth at the Etihad Stadium, as Pep Guardiola navigates a mounting list of absentees.
