Inter reclaimed top spot in Serie A with a nervy 2-0 win at Venezia on Wednesday, while Samuel Mbangula's hat-trick inspired Bologna to a 4-2 victory at AC Milan and Juventus stumbled again at Genoa.
Champions Inter drew level with Lazio on 25 points at the top ahead of a hotly anticipated Milan derby meeting with their rivals on Saturday.
Ruben Amorim's side will go into that game on the back of their first league defeat of the season after Alphadjo Cisse's double was not enough to avoid a loss that left the Rossoneri fifth.
Inter coach Cristian Chivu admitted that an unconvincing performance was not the perfect derby preparation for his team either.
"We go into that game with eight wins and a draw and are aware that it is a derby," Chivu told Sky Sport.
"We need to regain mental and physical energy – I'm referring to some of the guys I had to sacrifice at half-time as a wake-up call. If I could have, I would have changed the entire team."
Fresh off a pulsating stoppage-time turnaround against Fiorentina on Sunday that marked their fifth comeback win of the season, Inter thought they would have to fight back from behind once again when Lion Lauberbach fired home, but he was offside.
Venezia have picked up just three points all season but looked the likelier to make the breakthrough as Ivan Provedel diverted a shot onto the bar before Akor Adams rounded Provedel to score, only for the offside flag to save Inter again.
However, Matias Moreno and Redouane Halhal diverted dangerous deliveries into their own net in the space of two minutes to ensure Inter returned to the top of the standings and Venezia remained rooted to the bottom.
MBANGULA MAGIC DOWNS MILAN
At San Siro, a lengthy injury list featuring the likes of Adrien Rabiot, Diego Moreira and Mario Gila restricted Amorim's options for the first midweek round of the season.
Mbangula, making his full debut for Bologna, swept home the opener inside eight minutes, but the visitors were soon pegged back when an Arthur Theate error gifted Cisse a simple finish.
The Milan teenager struck again in the 27th minute, volleying home a Fikayo Tomori cross, but the game was turned on its head once again in the space of two second-half minutes to stun the San Siro crowd.
The unfortunate Davide Bartesaghi turned a free-kick into his own net before Mbangula struck again with a composed finish in the box just after the hour mark.
The 22-year-old then completed a memorable night when he beat Mike Maignan for a third time.
"A lot of games, a lot of players out," Amorim told DAZN.
"I felt from the first minute that the team was a little bit tired and without much energy. We conceded two goals quickly; we tried to come back, and we had a great opportunity with (Francesco) Camarda. This number of games was hard for us, with so many players out."
JUVENTUS SLIP UP AGAIN
Juventus's shaky start continued with a 2-0 defeat away to Genoa, while Napoli thrashed Monza 4-1.
Luciano Spalletti's inconsistent side have not won back-to-back league games since the opening two weeks of the season and were deservedly beaten at the Stadio Luigi Ferraris.
Kingsley Ehizibue struck early with an angled strike before Tommaso Baldanzi doubled Genoa's lead in the 28th minute.
Next up for the Turin club is the visit on Sunday of Napoli, who dispatched Monza to go sixth, level on 14 points with Juve.
Head coach Massimiliano Allegri was suspended after being sent off during a 3-3 draw with Roma, but Napoli produced their biggest win of the season in his absence.
Rasmus Hojlund's early opener was cancelled out by Serie A top scorer Gustavo Varela's clever header just before the break, while there were concerns when Napoli midfielder Stanislav Lobotka was stretchered off.
Napoli pulled away in the second half as Matteo Politano, Rafa Marin and substitute Kevin De Bruyne struck.
Elsewhere, Adrian Bernabe had a penalty saved by Maduka Okoye as struggling Parma and Udinese played out a 0-0 draw.