Both teams had their chances before Firmino used his nimble feet to create space and fire home after 37 minutes. Liverpool were the better side after the break, but Spurs wasted several excellent chances to tie things up.
Young defender Japhet Tanganga was thrown right into the fire for Spurs, making his Premier League debut against arguably Europe's most in-form team. The 20-year-old made an immediate impact, per the Athletic's Charlie Eccleshare:
Following Liverpool's early chances, both Lucas Moura and Son Heung-min tried their luck with shots that flew wide in the opening minutes. Dele Alli also had a go, but he blasted his effort over.
Firmino had a shot blocked after a promising attack, and Virgil van Dijk went very close to the opener, with Paulo Gazzaniga making an exceptional save to keep out his header.
Liverpool grew into the match as the half wore on, building momentum before finding the breakthrough. Jordan Henderson showed plenty of courage to bring the ball down with his head amidst the defenders, and Firmino did the rest, stepping past Tanganga before firing home.
Sports writer Duncan Alexander was reminded of those who doubted the Brazilian when he first arrived in England:
The final chance of the half fell to Spurs, but Lucas' header flew off-target. The Brazilian also whiffed with the first chance of the second half, although he was impeded by Henderson before he attempted his shot.
A well-worked Liverpool attack ended with Trent Alexander-Arnold firing wide, while Gazzaniga had to intervene to keep out Firmino. The Reds had the upper hand early in the second half, but Spurs had their moments, threatening through Alli.
A deflected shot from Son only narrowly went wide, while on the other side of the pitch, Mane forced a save from Gazzaniga after a quick counter. The play was started when Andy Robertson flew into Tanganga with a very dangerous tackle, but VAR opted not to intervene.
Lucas badly misplayed a counter that should have resulted in the equaliser, taking far too long before playing in Son and leaving his team-mate with little time to shoot. It was nothing compared to Giovani Lo Celso's miss from Serge Aurier's perfect cross, however.
The heavy press took its toll on Spurs, who visibly tired and were unable to make a late push for an equaliser. Divock Origi nearly doubled the lead late but ran into Gazzaniga before the final whistle.