SPAL hoped to put Juve’s title celebrations on ice, with the return of star striker Andrea Petagna, with Juve resting Cristiano Ronaldo among others and starting hotshot Moise Kean.
Following an even opening quarter, Juve grabbed the lead on the half-hour mark after Kean poked Joao Cancelo’s mistimed shot past Viviano.
Being restricted to few openings, Spal ended the half positively after Manuel Lazzari headed over the top 43 minutes in following a teasing cross.
With no changes at the break, SPAL were level on 49 minutes as Kevin Bonifazi towered home Pasquale Schiattarella’s inswinging corner.
Spal started to cause problems with their tails up, as Lazzarri moved down the right to pick out Alessandro Murgia who headed straight down the throat of Mattia Perin.
Juve made a change two minutes later, with youngster Hans Nicolussi brought on for Cypriot international Grigoris Kastanos.
The Italian champions closed in on a second after 72 minutes, but Paulo Dybala failed to make the most of Juan Cuandrado’s rebounded effort.
The home side stunned the champions-elect two minutes later, as Sergio Floccari swept Murgia’s ball into the far corner.
Juve searched for an equaliser with the introduction of Federico Bernardeschi late on, but it never came as SPAL clinch a first victory over Juve after 62 years.