A title-winning manager with Leicester, Ranieri is back in the Premier League as the latest man in charge of the Hornets, but it wasn't the start he would have hoped for as the experienced coach suffered the worst-ever defeat of his English top flight career.
Watford just had no answer as Roberto Firmino scored a hat-trick, Sadio Mane reached 100 Premier League goals and Mohamed Salah scored another solo stunner as Jurgn Klopp's men ran riot with a 5-0 victory.
It was a dismal performance from the hosts who were simply second best in every department, and it hasn't taken long for the bookies to react.
Much has been made of Watford's managerial merry-go-round following Ranieri's arrival as the club's 15th permanent manager over the last decade, and the 13th since owners the Pozzo family took control in 2012.
It's unlikely the 69-year-old will do anything to change the rapid-fire culture at the top, and bookmakers Betfair have reacted to the 5-0 drubbing by slashing the odds on Ranieri's departure from 33/1 to 10/1 as the next Premier League manager to meet his end.
His future is likely to depend on whether or not the former Chelsea, Leicester and Fulham boss achieves what he's been brought in to do - keep Watford in the Premier League.
But talkSPORT pundit Dean Ashton admitted that's unlikely based on their performances so far this season, unless the owners hand over funds for some January spending.
Asked if Watford have Premier League-quality players to stay in the top flight, former striker Ashton said: "No.
"I think he's going to do some business in January, and I think the owners will help him. They obviously need to keep hold of Ismaila Sarr, which will be difficult.
"But to judge him on this performance when Liverpool have been so good, I think that would be really, really unfair.
"He needs a couple more games to really implement what he wants and needs from his side to be harder to beat.
"That's what Watford were so good at last season in the Championship, especially at home. They were very hard to beat, they were very good defensively, and he's got to get them back to that.
"I think all the teams that came up are going to struggle at times this season when they come up against sides that are just so outstanding.
"This is a massive blip from Watford, and the teams that stay up are the teams that are able to wipe the really bad results away as quickly as possible, so then in bigger and more important games against teams in and around you - can you put in a performance against those sides?
"That's what Watford will be judged against, ultimately.
"Ranieri will wait, he'll be calm, he's got that experience, he'll need to work on a system they feel comfortable with, otherwise - like we saw in the first-half - if they're not sure, they're going to have no chance."
Watford got off to a shocking start against the Reds, with Ranieri admitting they were 'nervous' but things improved after Liverpool made a few changes in the second half, with the hosts looking more of a threat in the final 20 minutes.
And Ranieri was encouraged, with the manager telling talkSPORT he and the players will have to work hard to improve on their current position in 16th in the table.
"We started very nervously and some of their goals were our present," he told talkSPORT's Sam Matterface after the game.
"It was important for me to watch some better things, but we also showed some good things.
"Now I have to work hard and I hope my players follow me 100 per cent.
"Of course we lost this match badly - 5-0 is not so good - but I want to see more of the last 20 minutes. The last 20 minutes we played not badly.
"We have very tough matches, so we have to be very quick to understand what we are to do."
And he's not wrong - Watford's next seven games will see the struggling Hornets face Everton away, Southampton at home, Arsenal away, Manchester United at home, Leicester away, Chelsea at home and Manchester City at home.
Good luck, Claudio.