The promoted Watford was swept away by Liverpool (0-5), at the opening of the 8th day of the Premier League.
Mané opened the scoring for Liverpool (9th).
Firmino scored a hat-trick (37th, 52nd, 94th).
Salah had previously scored the Reds' fourth goal (54th).
Still undefeated provisionally takes the lead in the championship in front of Chelsea, who move at 6 p.m. on the lawn of Brentford.
To discover
Premier League fixtures and results
Premier League standings