With the game seemingly heading to a 1-1 draw after goals from Mo Salah and Son Heung-Min, Firmino produced a moment of real quality in the 90th minute, powerfully heading home from a corner to fire the visitors to a 2-1 victory.
Although still early in the season, the result could prove pivotal in the title race, with both sides battling it out for the top spot ahead of kickoff. Victory moves the reigning champion three points clear of its nearest rivals.
There was plenty of drama off the pitch, too, as the two managers, Jose Mourinho and Jurgen Klopp, were involved in a touchline exchange that seemingly ended amicably.
“I told him the best team lost,” Mourinho told Amazon Prime. “He disagreed but that’s his opinion.
“By the way, if I behave the same way on the touchline like he does, I have no chance to stay there […] for some reason I am different.”
Klopp said there was “no argument” between the two men at full-time and added that his side deserved the late winner, in particular praising Firmino for just his third league goal of the season.
“It was a really, really good game from us. It’s exactly the way you have to play. You have chances, you score the goal,” he told BBC Radio 5 Live.
“I love talking about Bobby’s [Firmino] goals but it always sounds like we are shocked […] it’s not that rare that he scores.
“He’s a top-class player and he scores goals but he has some things to do for us which sometimes keep him outside of the box for us. I couldn’t be more pleased for him and for us because it was a top goal and very important.”
Liverpool is now unbeaten in its last 66 league games at Anfield, but it could have easily lost that record on Wednesday.
As expected, Mourinho set his side up to punish Liverpool on the counterattack and his game plan almost paid off.
Steven Bergwijn hit the post and Harry Kane missed from close range in a dramatic few minutes in the second half, but the visitor was left to rue missed opportunities.
“So close to winning, not so close to a draw,” added a visibly frustrated Mourinho.
“We missed the chances, we had the chances, had the game under control. A draw would be a bad result so you can imagine how we feel with a defeat.
“Very good performance, of course some mistakes, some things to improve, a very unfair result.
“Today, Liverpool didn’t look like a team that is champion, European champion, world champion. That difference was not on the pitch.”
Liverpool took the lead in the first half when Curtis Jones drove into the Tottenham penalty area and found Salah, whose deflected shot looped into the back of Hugo Lloris’ net.
Tottenham soon responded with a typical counterattacking move finished by Son — like Salah, his 11th Premier League goal of the season — but Firmino’s late header ultimately settled the contest.
The 73-year-old is credited with transforming the club during his successful reign, winning a treble in the 2000-01 season.
Liverpool now faces a tough test away to Crystal Palace next in the Premier League whilst Spurs host Leicester City.