Juventus crashed to a humiliating 2-0 defeat at Cagliari on Wednesday, days after sealing their ninth consecutive Serie A title, prompting coach Maurizio Sarri to consider fielding his Under-23 team in Saturday's finale to conserve resources ahead of their Champions League challenge.
Cagliari's 20-year-old forward Luca Gagliano tapped in the opener eight minutes into his first Serie A match, beating veteran Juventus keeper Gianluigi Buffon to score his first top division goal.
And the young Italian then teed up Giovanni Simeone in first half stoppage time to give Cagliari their first win over Juventus in 11 years.
"The 40 goals conceded (this season) may be a concern, but tonight's game is not," said Sarri.
"We had nine injured and we came from a championship won 68 hours ago, so it was an atypical game that should be taken for what it is.
"We are the only ones in Europe who have played five games in 12 days, the League has created big problems for us.
"Let's see how we are tomorrow and if it is appropriate to line up the Under-23 team on Saturday against Roma to recover better."
Cristiano Ronaldo missed the chance to keep pace with Serie A's leading scorer Ciro Immobile, the Portuguese now four goals behind the Lazio forward's tally of 35 with one match remaining.
The five-time Ballon d'Or winner had a goal ruled offside after 16 minutes and was denied twice by Cagliari goalkeeper Alessio Cragno as the 13th-placed Sardinians ended their eight-match winless run.
It was a worrying performance for Sarri's side, who have won just two of their last seven games, with key forwards Paulo Dybala and Douglas Costa fighting for fitness ahead of the Champions League showdown with Lyon on August 7 in Turin, when they need to overturn a 1-0 first-leg deficit.
Immobile on target
In Rome, Immobile moved to within one goal of equalling the Serie A single season scoring record as Lazio beat relegated Brescia 2-0 to stay in the race for second place.
Immobile struck eight minutes from time to close in on Gonzalo Higuain's record of 36 goals, scored for Napoli in 2015-16.
Lazio are fourth, equal on 78 points with third-placed Atalanta, who beat Parma 2-1 on Tuesday, and one adrift of Inter Milan who are second following their 2-0 win over Napoli.
Inter and Atalanta will go head-to-head this weekend with Lazio's last game at seventh-placed Napoli.
Immobile helped Joaquin Correa open the scoring after 16 minutes at the Stadio Olimpico, with Correa returning the favour late on.
Behind the top four, who are assured of Champions League football next season, Roma sealed their Europa League group stage berth with a 3-2 win at Torino.
Napoli have already secured their place as a result of their Italian Cup win while AC Milan, who will finish sixth, must go through the Europa League qualifying rounds despite beating Sampdoria 4-1.
Zlatan AKA 'Benjamin Button'
Stefano Pioli's side remain four points behind Roma after Zlatan Ibrahimovic scored twice and set up a third in a dominating display against Samp.
The 38-year-old got his head to an Ante Rebic cross within four minutes in Genoa for his fastest goal in the Italian top flight, before nodding the ball across for Hakan Calhanoglu to add the second six minutes after the break.
Turkish winger Calhanoglu provided the cross which allowed Ibrahimovic to add his second of the night.
Leao added a fourth in injury time as Milan extended their unbeaten run to 11 games.
Ibrahimovic has scored nine league goals since rejoining Milan in January.
The veteran brings his club tally to 51 goals for the club, combined with his previous stint between 2010 and 2012.
He also becomes the first player to have scored 50 goals for both Milan clubs, with 57 netted during his time at city rivals Inter from 2006 to 2009.
"Like Benjamin Button, I've always been young, never old," said Ibrahimovic of the film of a man who ages in reverse.
"They tell me I'm old and tired but I'm just warming up."
Lecce's bid for survival will go down to the final day after they came from behind to beat Udinese 2-1.
The southern club occupy the final relegation position but are now just one point behind 17th-placed Genoa, who were hammered 5-0 at Sassuolo.
Both Lecce and Genoa will face Parma and Hellas Verona respectively at the weekend hoping to avoid joining Brescia and SPAL in Serie B.