A deflected first-half strike from Mohamed Salah put the champions into a deserved lead on Wednesday night, but Son Heung-Min quickly drew the visitors level.
However, the Reds would prevail thanks to Firmino’s late intervention - the No.9 expertly guiding Andy Robertson’s inch-perfect corner past Hugo Lloris with a header of power and precision.
Here are five talking points on another Anfield evening to savour…
The Reds are top of the league
The continuation of a perfect top-flight home record this season - seven matches, seven wins - saw Liverpool overtake Spurs at the top of the table.
Having gone into Wednesday’s clash separated from Jose Mourinho’s team by goal difference alone, the Reds produced a performance described as ‘outstanding’ by their influential captain to overtake their opponents.
Jürgen Klopp’s side now sit three points clear of Tottenham, and four ahead of Southampton and Leicester City, and will guarantee their spot at the summit on Christmas Day by avoiding defeat at Crystal Palace on Saturday.
Academy lads shine bright
Both aged just 19, Curtis Jones and Rhys Williams rose to the occasion and delivered displays of assured maturity against high-class opposition.
Premier League debutant Williams was a calm and measured presence in partnership with Fabinho at the back, while Jones prompted and probed during an impressive all-round central midfield performance that was acknowledged with the Man of the Match award.
Williams led the way for Liverpool in terms of clearances (three) and won all 15 of his eight duels and seven aerial duels throughout the 90 minutes.
His fellow Academy product Jones was a constant force throughout the game, both in offensive and defensive play.
No player made more successful passes (105) or passes in the opposition half (87), and only Robertson and Jordan Henderson enjoyed more touches of the ball.
On the other hand, Jones regained possession on nine occasions, made four interceptions and took on 13 duels - a tally bettered only by Sadio Mane and Salah.
Bobby settles it… again
An eye-catching statistic emerged from Wednesday’s win.
As noted by football writer Andrew Beasley, the victory represented the Reds’ 50th by a single goal in the Premier League under Klopp.
Twenty-six of those successes have ended 2-1, with 1-0 (on 16 occasions) the second-most common scoreline.
Firmino’s contribution to these narrow wins has been enormous. The Brazilian netted the decisive goal in 10 of the 50 one-goal victories - the most of any Liverpool player - and Klopp surmised post-match: “He scores goals, important ones for us.”
That he does.
Deja vu
In each of the last three seasons, Liverpool have conjured late goals to beat Tottenham 2-1 at Anfield.
In 2018-19, Toby Alderweireld’s 90th-minute own goal secured the points for the Reds, while last term Salah’s penalty sealed a comeback victory after Henderson had equalised Harry Kane’s early opener.
Firmino’s outstanding last-minute header extended that particular sequence to include the current campaign, too, and also means Klopp’s side have now recorded five consecutive Premier League wins over Spurs.
Each of those games have been settled by one goal, with Firmino responsible for the last two.
More capital gains for Mo
Salah’s strike maintained a prolific run of goalscoring form, with the Egyptian having now netted 18 times in his last 18 home Premier League matches versus clubs from London.
Against Tottenham, the No.11 has registered six goals in eight Liverpool appearances and his opener on Wednesday means he shares pole position in the race for the Golden Boot with Son and Dominic Calvert-Lewin.
With 11 goals in 12 top-flight appearances, and 14 in 20 overall, Salah has begun 2020-21 in typically lethal fashion.