Trent Alexander-Arnold had one goal and two assists as Liverpool secured a 4-0 win over Leicester City on Thursday and increased their lead in the Premier League standings to 13 points.
The win at King Power Stadium on Boxing Day gives Liverpool even more breathing room in their quest for their first domestic league title in 30 seasons.
Second-place Leicester City entered the match with the chance to decrease Liverpool's lead into single digits, but the Foxes weren't able to penetrate a stout Liverpool defence.
Defending champions Manchester City are poised to jump over Leicester in the standings should they win their match on Friday against Wolves.
"We played really good football after all the travelling and intense period, yes it is the best performance of the season and we controlled it, to get four goals is something to be proud of," said Alexander-Arnold.
"You don't really think you will be 13 points clear but we are happy to be in this position and we won't take it for granted. This is the Premier League and anything can happen," he added.
Firmino's first goal came into the 31st minute when Alexander-Arnold sent in a pinpoint cross to the far post, allowing the Brazilian to leap across goalkeeper Kasper Schmeichel for the goal.
Milner doubled the lead in the 71st minute after Leicester defender Caglar Soyuncu was booked for a handball, and the veteran made no mistake about it with a clean take from the spot.
Alexander-Arnold and Firmino connected again three minutes later when the Englishman threaded a ball into the penalty area for Firmino to then take a shot.
Capping off a stellar performance on the night, Alexander-Arnold earned his goal when he was left unmarked and dispatched a low shot assisted by Sadio Mane.
"It's one of many successful nights so far this season," said Milner. "We are not even halfway. So much can change and happen. The strength of this team is we tale it one game at a time."