Bosnian midfielder Pjanic had an effort tipped on to the crossbar.
Pjanic afforded Mandzukic the first chance of the match with the Croatian powering his half-volley over the crossbar from the edge of the box and were given a helping hand to move ahead when Hetemaj headed Pjanic's teasing free-kick past his own keeper.
Allegri rotated his side giving first starts to Polish goalkeeper Wojciech Szczesny and midfielders Douglas Costa and Blaise Matuidi.
The Argentine then added the third himself seven minutes from time - his fifth goal this season in Serie A.
The 23-year-old also set up Juve's second goal for Gonzalo Higuain after he came on as a second-half substitute and his performance earned glowing praise from coach Massimiliano Allegri.
There is plenty of action on Sunday, starting with joint Serie A leaders Inter taking on surprising new boys Spal, who are still unbeaten this season, at 11.30 United Kingdom time (10.30 GMT). "His future is with Juventus and I am very happy with that".
"Last season we played 57 competitive games, on top of internationals, so there are naturally some problems to consider", Marotta told Mediaset Premium.
"We let Chievo have a few too many shots: 11".
"Definitely Dybala's entrance brought freshness".
"The team was winning when I came on and there were spaces to play in", Dybala said.
The champions could be joined on Sunday at the top of the table by AC Milan, Inter Milan and Napoli depending on weather conditions which forced the postponement of Saturday's game between Sampdoria and Roma in Genoa. "From 2-0 onwards it was all the more hard for us".