The Reds are still well on course for a first league title in 30 years with a commanding 22-point lead at the top of the table.
But they were beaten for the first time in 45 Premier League games and in comprehensive fashion at Vicarage Road as Ismaila Sarr’s double and Troy Deeney’s measured finish completed a famous win for Watford.
“Of course sometimes a little knock is important,” said Klopp. “So I don’t see anything negative in it. From time to time if you are not good enough you need to see effect.”
The Club World Cup and Uefa Super Cup have already been claimed, while Klopp’s men travel to Chelsea in the FA Cup fifth round on Tuesday and trail Atletico Madrid 1-0 from the first leg of their Champions League last-16 tie.
“We can start again with whatever we did before, and we will,” said Klopp. “We cannot say now we will react in this way or that. We have to show it in the next games.”
Dejan Lovren was one of those blamed by the Liverpool support for a rare defeat as Deeney relished the battle with the Croatian international.
“Maybe it is a wake-up call for us,” he said. “It can be a benefit to help us get to the end of the season.
“We know there is always an end for everything. It is here where our unbeaten run ended. We will not look at this result and think it was a bad season because of losing here. One performance won’t ruin everything, but this is always a learning process.
“The last couple of games hadn’t been the best performances but we won. This one, it didn’t happen. This one was like someone hit us in our faces – and we deserved it.”