The forward became Liverpool's youngest-ever goalscorer at the age of 17 years and 45 days after scoring in front of the Kop in the 2-0 EFL Cup victory over Leeds on Tuesday. The Liverpool manager had responded by telling Lucas that every player would.
He said: "It's not always easy when you know you're not playing, but you train for yourself to make sure you stay fit and be ready".
Leeds, whose last League Cup semi-final appearance was in 1996, should have been ahead early on when Hadi Sacko broke the offside trap and saw his shot saved by Simon Mignolet.
"For me, it's disappointing because Phil Coutinho was in very big form, but when I came on the pitch I thought about doing my thing and enjoying my game".
Klopp also praised 18-year-old right-back Trent Alexander-Arnold, who crossed for Divock Origi's goal, and 19-year-old midfielder Ovie Ejaria.
"Rightly so, he scored an important goal".
"Congratulations not only to him but all the young boys - when they come in, they take their chance and they show that they've got a lot of talent".
Origi has now scored in successive games, and Mignolet believes his countryman is reaping the rewards of the work he is putting in at Melwood.
"I am really happy with him, the only problem is I am a little afraid about you (the press)".
Kevin Stewart - 7/10: The youngster showed good positional awareness and prevented much of Leeds' attacks through the middle except for the one time he let Kemar Roofe through on goal, he was confident in possession and did well before he had to be substituted in the final 25 minutes due to injury.
Klopp's men have won nine of their first 13 league games, with Burnley the only side thus far to take all three points off the Reds, and are the top-scorers in the division with 32 goals, three more than the next best Chelsea and City. Aged 17 years and 226 days, he came off the bench to score a last-gasp victor against Aston Villa - a strike that helped United clinch the title. But on the other hand, we only bring him in because we want to use him.