Napoli almost squandered the chance of setting a club record of 11 consecutive Serie A victories within a season when Udinese substitutes Ilija Nestorovski and Lazar Samardzic both scored late in the game.
"Every victory is a struggle, and the final 15 minutes of this game help to underline just how much these players have achieved so far is not to be taken for granted," Spalletti told DAZN.
"We thought the game was over and took our foot off the gas, but the game is never over because when you can introduce players off the bench like Nestorovski, they can find a way through if you don't keep the tempo up."
Napoli go into the World Cup break top of the Serie A standings, with their next game to come in early January, but Spalletti was still cautious about talk of winning the league.
"There are six challengers and they are all close by, because it just takes a couple of incidents, a couple of minutes to create problems," he said.
"This afternoon's match will help us because it hasn't happened so far, but we need to be even more determined and committed to the end in every match."
