Massimiliano Allegri's men dropped points for the third time in four Serie A matches on Tuesday as they were held to a 1-1 draw by Inter in their first game back after the mid-season break.
Juve's lead was cut to a point as a result of Mauro Icardi's second-half equaliser, with the draw following on from stalemates with Fiorentina and Sampdoria late last year.
With the Italian champions now just a point clear of second-placed Roma and facing two tricky UEFA Champions League last 16 meetings with Borussia Dortmund, Buffon urged his team to refocus.
Specifically, the legendary captain feels Juve must begin to kill off games if they are to claim a fourth straight Scudetto.
"We need to mature if we're going to be where it counts, particularly in the Champions League," he told reporters.
"There are moments in games when we dominate [and] create a high number of chances, but until we get that all-important second goal, [we need to be] on [our] guard - especially against a side like Inter.
"We all knew that this was another golden opportunity to extend our lead at the top. But we didn't take it and we're disappointed."
