Having started the game on the front foot, the Reds raced into the lead through Mane’s well-taken ninth-minute opener. The rest of the half played out in much the same fashion, with Liverpool doubling their advantage through Firmino in the 37th minute.
The Brazilian doubled his tally soon after the restart before Salah lit up the tie by adding a sumptuous fourth two minutes later. Virtually assured of the three points, Liverpool then took their foot off the gas for most of the second half.
However, a late foray forward saw Firmino complete his hat-trick as he wrapped up the rout for the Reds. In the process, Liverpool dealt Ranieri his worst defeat in the English top flight.
On that note, here are the Liverpool player ratings from their dominant display.
Drafted in to replace the quarantining Alisson, Kelleher was only marginally more involved in the game than his absent teammate. Rarely called into action, the Irishman registered one of the most comfortable clean sheets of his fledgling career.
Alexander-Arnold, given the freedom of the right flank on his return from injury, took full advantage of that in an excellent attacking display. The Englishman was taken off just after the hour mark as Liverpool looked to rest key players ahead of a tough run of fixtures.
Barely troubled by Watford’s attackers, Matip regularly brought the ball out from the back with calmness and confidence. The classy centre-back completed the most passes (101) in the game, racking up an impressive 93% pass accuracy to boot too.
Van Dijk was a rock in the Liverpool defence, hardly allowing anything to go past him on the rare occasions Watford ventured forward.
The Scotsman was a livewire down Liverpool’s left flank, constantly bombing forward in support of his attackers. Like Alexander-Arnold on the opposite flank, Robertson was given an early breather with more demanding games on the horizon.
The ageless Milner started the game in midfield, marking a characteristically energetic display with an assist for Firmino’s goal. In the process, he became the oldest Liverpool player to provide an assist in the Premier League.
He then showcased his versatility by slotting in at right-back for a while before going off late on in the game. During his time on the pitch, Milner created more chances (4) and made more interceptions (2) than any of his Liverpool teammates.
Playing the deepest of Liverpool’s midfield three, Henderson turned in a solid performance, winning tackles and keeping the ball moving swiftly.
Keita delivered another busy performance, making an impact at both ends of the pitch without really grabbing the headlines.
Salah started the game like a man on a mission, and continued in the same vein, tormenting Danny Rose throughout the game. The Egyptian marked a spectacular display with a gorgeous assist and a second breathtaking goal in as many games.
Often the man whose unselfish play helps his fellow attackers reap the rewards, Firmino filled his boots on this occasion. The Brazilian striker bagged an excellent hat-trick in addition to claiming the assist for Salah’s strike. It was only the second hat-trick of his career, with Firmino becoming the Brazilian to net multiple Premier League hat-tricks.
Mane set Liverpool on their way with a landmark 100th Premier League goal, and looked threatening throughout, also setting up one of Firmino’s three strikes. Incredibly, none of Mane's strikes in the competition have come from the spot, making him only the third player in Premier League history to achieve the feat.
Tsimikas replaced Robertson midway through the second half, but struggled to make as much of an impact in the game.
Oxlade-Chamberlain showcased energy and desire in his second-half cameo without making too much of an impact on proceedings.
On for the final five minutes, the young Welshman found the time to grab an assist as he set up Firmino’s third.