Liverpool staved off the threat of Watford's 'new manager bounce' with a comfortable 5-0 win at Vicarage Road.
Claudio Ranieri's first game as Hornets manager could barely have gone any worse as his new side were picked apart from start to finish on Saturday, while their visitors head back to Merseyside top of the Premier League for a few hours at least.
Sadio Mane opened the scoring for the visitors after just eight minutes. Mohamed Salah outmuscled Danny Rose with ease to win a loose ball and curled a beautiful ball round the back of the defence to his Senegalese teammate, which was easily converted from close range.
Salah was denied a goal of his own twice soon after, with Ben Foster palming a driven shot wide and Rose making a vital block on the edge of his six-yard box.
Watford spent much of the first half trying and failing to even get out of their own half, but created their first real chance when Ismaila Sarr slipped through Cucho Hernandez, only for the forward to be denied at the last by Trent Alexander-Arnold.
But Firmino doubled Liverpool's lead 10 minutes before half-time. Mane's reverse pass found an overlapping James Milner, and he played a simple ball across goal for the Brazilian to bury.
Salah again came close to getting on the scoresheet just after the break, with Foster again stretching to deny him. The Reds did find their third moments later, however. Andy Robertson's teasing cross towards Salah was sent goal-bound by Watford's Craig Cathcart and Foster had to be alert to prevent the own goal, but Firmino was on hand to tap in the rebound.
Mane and Salah both nearly added a fifth before Sarr rattled the post at the other end, and Firmino grabbed his hat trick in the sole minute of stoppage time as the Reds cruised to the three points.
Watford player ratings
1. Goalkeeper & defenders
Ben Foster (GK) - 5/10 - Made a couple of good saves to stop the scoreline getting out of hand...any more than it already did.
Kiko Femenia (RB) - 4/10 - Initially dealt well with Mane, but then proceeded to be given the run around like the rest of Watford's defenders.
William Troost-Ekong (CB) - 4/10 - Imposing and yet still very ineffective, an impressive feat.
Craig Cathcart (CB) - 2/10 - Couldn't pass and couldn't defend. Liverpool had plenty of joy pulling him out of position.
Danny Rose (LB) - 2/10 - Salah chewed him up and spat him out. Not a performance that he'll be keen to watch back.
Emmanuel Dennis (RM) - 4/10 - A bit lost playing on the wing instead of centrally. Runs were all over the place and his passing was poor.
Juraj Kucka (CM) - 2/10 - Absolute nothing in midfield.
Moussa Sissoko (CM) - 5/10 - Had the physicality to do Kucka's work for him, but still needed support to progress the ball up the pitch.
Adam Masina (LM) - 3/10 - Probably picked to try and help clamp down Liverpool's right flank. It didn't go well and he was replaced at half-time.
Cucho Hernandez (CF) - 4/10 - Made several good runs but was scarcely found by his teammates.
Ismaila Sarr (CF) - 4/10 - Ditto, but with added take-ons and dribbles.
Tom Cleverley (CM) - 4/10 - Not sure what this substitution was meant to do, but whatever it was, it didn't work.
Jeremy Ngakia (RB) - 5/10 - Wasn't embarrassed. Good job.
Joao Pedro (CF) - 5/10 - Played with intent and bite, which is more than could be said for many of Watford's starters.
Liverpool player ratings
5. Goalkeeper & defenders
Caoimhin Kelleher (GK) - 6/10 - Pretty much nothing to do in goal. Can dust his hands off and declare it a job well done.
Trent Alexander-Arnold (RB) - 7/10 - Some neat touches and passes without ever needing to create too much.
Joel Matip (CB) - 7/10 - Calm and collected, as opposed to his opposite numbers.
Virgil van Dijk (CB) - 8/10 - What a defender, looked every bit back to his best today.
Andy Robertson (LB) - 8/10 - Got stuck in at both ends of the pitch and his energy helped the cause.
Jordan Henderson (CM) - 6/10 - Didn't have to do too much because Watford's midfield was hopeless.
James Milner (CM) - 7/10 - Started the game off the pace, but grew into his role and grabbed an assist.
Naby Keita (CM) - 6/10 - Same as Henderson, one of the easiest games he'll ever play.
Mohamed Salah (RW) - 10/10 - The best player in the Premier League. Rose will be having nightmares for weeks.
Roberto Firmino (CF) - 10/10 - Did his chances of regaining his place in the lineup in the long-term the world of good with two poachers' finish.
Sadio Mane (LW) - 9/10 - Vintage Mane, today. Played with such enthusiasm and exuberance, a joy to watch.
Kostas Tsimikas (LB) - 6/10 - Did well to replace Robertson's energy.
Alex Oxlade-Chamberlain (CM) - 6/10 - One of his better midfield cameos.
Neco Williams (RB) - N/A