Arne Slot witnessed Liverpool's second-string side nearly squander a two-goal advantage before securing their spot in the Carabao Cup semi-finals.
Darwin Nunez and Harvey Elliott had put the Premier League frontrunners comfortably ahead within the first 30 minutes against a battling Southampton team.
However, Cameron Archer's superb strike narrowed the gap before goalkeeper Caoimhin Kelleher thwarted Archer's attempt at an equaliser at close quarters, while Paul Onuachu and Ben Brereton Diaz missed chances to level late in the game.
"The first half was really good, a good performance," Slot remarked, with his squad now on a 20-match unbeaten streak.
"But it didn't come as a complete surprise to concede because we got a bit sloppy and lost one or two easy balls. They came back into the game."
Serving a one-game touchline suspension, Slot opted to rest Virgil van Dijk and Mohamed Salah, giving 17 year old Trey Nyoni his debut start. Tyler Morton, another product of the academy, was in the starting lineup, and Jaden Danns and James McConnell made appearances from the bench.
Slot praised his young talents: "This club is known for this. These players train with us on a daily basis and it is nice to see they showed they can play at this level. Now the next step is to be capable of playing [regularly] for Liverpool."
He added, "We have to defend the trophy. I wasn't involved but the players were. We want to compete in every competition. It's always a tough competition but this year for sure."
Interim Southampton boss Simon Rusk has admitted he's uncertain if he'll take the helm against Fulham, yet he commended his squad's resilient character following their 5-0 drubbing by Spurs which resulted in Russell Martin's departure.
"Our priority going into the game was to be hard to beat, given the nature of Sunday," Rusk commented.
"The players reflected on the change as people and professionals to prepare for the next game."
He also noted, "I'm sure one or two of them were disappointed but we have a responsibility to try to win the next game. Their receptiveness to me has been second to none."