The Portuguese forward converted from close range in the third minute of first-half added time, turning in Andrew Forson's low cross to settle a tight last-32 tie at the Stadio Olimpico Grande Torino. Monza will now travel to face AC Milan in the next round.
Torino had the better of the opening exchanges, with Gaetano Oristanio striking the post inside the first minute, before Monza gradually took control. The visitors were denied a first-half penalty after Perenzoni initially pointed to the spot for a foul on Bakoune, only for VAR to overturn the decision for an offside in the build-up. Mota then struck the crossbar with a header before finding the breakthrough in stoppage time.
Torino head coach Ignazio Abate, speaking to Italia 1 after the match, felt the disallowed penalty was a harsh call.
"The penalty that was overturned looks very similar to the one Vlasic conceded against Milan. For me it's a penalty, but if that's the standard being applied, it's right not to award it," he said.
Asked whether Monza's win was deserved, Abate did not dispute the result.
"I agree. We started well and tried to press them and move them around the pitch for the first half hour. Then Monza took control of the game and we stopped sensing the danger. We need to grow, become a team, and there's a lot of work to do. Fortunately the transfer window is over, we need to change direction," he said.
Mota, whose goal was his 41st for Monza and came while wearing the captain's armband, said the priority now shifts to the club's next task.
"I'm very happy about the goal, but especially about the win," Mota told Italia 1. "The game against Milan will be a great one. We already played well last Saturday with plenty of chances, and working like this we'll get many more points. Let's enjoy the win and then think about the league."
Juric, returning to the stadium where he spent three seasons as head coach, praised his young side's application.
"We didn't need a response today, because we also played a great game against Udinese. Today was even better, and I'm pleased because we had so many very young players out there. Everyone put in a great performance," he said, before turning to Robinson's display on the left flank.
"I found him in Southampton's second team, and there was a chance to take him on loan, so we did. Today he did a lot of good things. He has enormous potential and really outstanding qualities, even though he isn't fully developed physically yet."