The club legend, who is set to leave Turin at the end of the season, came off the bench to score a crucial goal to keep the Bianconeri in pole position in the Scudetto race
With the game tied at one goal apiece after Stefano Mauri cancelled out Simone Pepe's opener, the Juve legend was sprung from the bench and rolled back the years with a characteristically deadly set-piece which propelled his side back to the summit of Serie A.
AC Milan had reclaimed top spot the night before with their victory over Chievo in Verona but the Bianconeri began as if intent on sending a message to their title rivals.
Juve could have opened the scoring as early as the fifth minute but Fabio Quagliarella was just off target after sliding to get himself on the end of Giorgio Chiellini’s cross from the left-hand side.
The hosts continued to dominate thereafter and really should have broken the deadlock on 28 minutes when the ball broke for Pepe in the area but he shot straight at Federico Marchetti.
However, Pepe made amends just over 60 seconds later, controlling a clever chip from Pirlo on his chest before then volleying home acrobatically in one glorious movement.
The Bianconeri were now buzzing and had it not been for Marchetti, the game would have been over by the break, the Biancocelesti goalkeeper scrambling back to keep out Arturo Vidal’s stunning strike before then stretching out a hand to deny Quagliarella after being wrong-footed by the forward’s deflected shot.
As it was, the two sides went in level at the interval, with Mauri beating Gigi Buffon with a bullet header after Juve's three-man defence, which had been so dominant up until that point, had gone AWOL.
Credit to a shell-shocked Juventus, they regrouped during the break and quickly set about reasserting their superiority after the restart.
However, while they were dominating possession once more, they struggled to open their opponents up and were restricted to long-range efforts from Quagliarella and Claudio Marchisio.
Stephan Lichtsteiner did fluff his lines after being the recipient of a sublime pass from Vidal but there was an inescapable suspicion that the hosts had run out of ideas.
However, cometh the hour, cometh the man, and with just eight minutes remaining substitute Del Piero curled home a free kick to secure a victory which moves Juve two points clear of Milan once more. As for Lazio, who lost Libor Kozak to a red card right at the death, they remain third.