Needing to overturn a 5-2 deficit from the first-leg of their Champions League playoff, Juve took the tie into extra-time before Gala struck twice to end the second-leg 3-2 in Juve's favour.
Gala move into the round of 16 7-5 on aggregate and Di Canio stated afterwards: "Juventus must feel the pain of not getting through, but only in the first leg.
"At 3-2 they should have defended like they did in the '70s, but the feat, with a great show of energy, was almost achieved.
"The applause from the crowd was wonderful; it was a Juve that thrilled us, because feats always have that effect, but we certainly can't forget what happened last week."
Di Canio added: "Certainly, from a performance and a match like this, we can see who will be able to be part of Juventus tomorrow."