It may only have been a friendly between the Italian arch rivals, but tempers threatened to boil over at times, especially in a feisty second half in stifling Nanjing.
The game ended 1-1 after 90 minutes, with Cristiano Ronaldo drawing Juventus level with a deflected second-half free-kick following De Ligt's own goal on 10 minutes.
Ajax teen Matthijs de Ligt to join Juventus
Then the 41-year-old Buffon -- more than twice De Ligt's age -- sprang to the fore in the shootout, making a triumphant return to the Serie A champions after a year with Paris Saint-Germain.
Dutch teenager De Ligt, who joined Juventus last week from Ajax for a reported 75 million euros ($85 million), came on as a substitute during Sunday's 3-2 defeat to Tottenham Hotspur in Singapore.
New Juventus coach Maurizio Sarri named the 19-year-old to start in the "Derby d'Italia", but the central defender got off to the worst possible beginning, directing the ball past goalkeeper Wojciech Szczesny with his knee to give Inter the lead.
De Ligt, who was one of the most coveted players in world football before sealing his big-money move, was largely untroubled for the rest of the half before being substituted at the break.
It was only a pre-season friendly as part of the International Champions Cup, but Antonio Conte's Inter dealt out some rough treatment to Ronaldo.
Veteran Buffon returns to Juventus after year at PSG
Three times in the first half, in a match played in sweltering conditions in eastern China, the Portuguese forward was sent sprawling to the turf.
There was a flashpoint in the 51st minute when Juventus substitute Merih Demiral -- who was to score the winning penalty -- lashed out while waiting for his side to take a corner.
Minutes later skipper Leonardo Bonucci talked himself into a yellow card as the referee struggled to regain control.
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