Dembele also saw a shot go just wide, but overall it was a boring game with Huesca unable to seriously challenge Ter Stegen in the Barca goal.
"There is pride and confidence, but if we do not win we are stuffed". The team sits at the top of La Liga with a comfortable advantage over seconds Atletico Madrid, are headed for the Copa del Rey final, and their chances at getting through the next round of the UCL are higher than they have been in a couple of seasons.
Defender Leonardo Bonucci was also rested along with Blaise Matuidi, Alex Sandro, Mario Mandzukic and Miralem Pjanic, with forward Federico Bernardeschi coming off the bench late in the game.
"It is very hard over the course of a season to always be at the highest level", said Valverde. "We played with a lot of youngsters". The match against Huesca presents an opportunity to prove why he deserves more game time at the club.
Kean opened after half an hour with Joao Cancelo pushing through the right with his shot going wide before the teenager stuck out his foot to redirect the ball home.
Four players were handed their La Liga debuts for the runaway leaders in an uneventful game.
Bonifazi headed in a corner at the near post four minutes into the second half, and that would still have been enough for Juventus to clinch the title, but Floccari scored the victor in the 74th off Alessandro Murgia's cross.
Juventus beat SPAL 2-0 in November.
"Congratulations to the lads, now we must find continuity", said Milan coach Gennaro Gattuso.
What this means is clear Messi has a far greater shot at glory in 10 weeks' time than his old rival Ronaldo.
But SPAL held on to move up to 13th, seven points above the drop zone, having already beaten Champions League-chasing Lazio and Roma.
Much has been made of Luis Suarez's Champions League scoring drought on the road, and while the Uruguayan has still not officially netted an away goal in the competition since September 2015, he had a huge hand in Barca's victor.