However, Dembele was by no means at his scintillating best in what was a dour 0-0 draw - which was perhaps unsurprising, given he was surrounded by so many bit-part players, chief among them Kevin-Prince Boateng.
It was a first top-flight win over Juventus for Spal which has gone through bankruptcy and been refounded twice - in 2005 and 2012.
Barcelona were held to a 0-0 draw at Huesca but Ernesto Valverde's side, with star players including Lionel Messi and Luis Suarez rested for next week's Champions League game against Manchester United, still moved 12 points clear of Atletico Madrid. "We will make changes but with the aim of putting out a competitive team". "I didn't realise at the time actually that I caught him like that".
The defending Spanish champions host United on Tuesday in the return leg of their Champions League quarterfinal.
But before they take on Ole Gunnar Solskjaer's side, they face Huesca, who are six points from safety at the bottom of La Liga with seven games to play. Their survival bid remains unlikely but alive.
Dembele came closest to a goal in the first half after a brilliant reverse pass from the talented Riqui Puig, one of a number of youngsters given a chance to impress.
Santamaria was at it again as he guided Jean-Clair Todibo's header into touch a minute later following a cross into the penalty area.
Huesca replaced Juanpi with Gonzalo Melero, whose first act was to get in a header that was straight at Barca keeper Marc-Andre ter Stegen, and then Juam Camilo Hernandez came on for David Ferreiro.
"And then the victor of City-Tottenham, as we were saying, is an English team that reaches a semi-final and goes to play against Juventus or Ajax so I really used to say this all the time when you get into a semifinal you have 12.5 per cent possibility equally to win the competition".