Napoli striker Lorenzo Lucca was handed just his second start of the season after Rasmus Hojlund was ruled out with illness, and the 26-year-old almost gave his side an early lead when his seventh-minute header was clawed away by Guglielmo Vicario.
The Partenopei were looking to continue a prolific run of 11 goals in their previous three matches (W2, D1), but that was the only time they worked the Juventus goalkeeper before half-time, despite enjoying a greater share of possession.
The Bianconeri were similarly blunt in attack, although they did go close to breaking the deadlock when a 28th-minute corner hit Juan Cabal – making his first Juve start since February – and struck the far post.
It sparked a rush of chances as Noa Lang and Alajbegovic blazed over in quick succession, before the latter forced Alex Meret into his first save of the night when his low drive was pushed away in the dying seconds of the half.
Both managers responded to the underwhelming opening 45 minutes by making changes at the break, with Federico Gatti replacing Weston McKennie for the hosts.
Meanwhile, Marco Landucci – leading Napoli with Massimiliano Allegri serving a touchline ban – brought on Amir Rrahmani and Billy Gilmour for Giovanni Di Lorenzo and Kevin De Bruyne.
However, the substitutions failed to have the desired effect, with neither team looking particularly threatening.
Juve might have continued their record of failing to score in the opening 15 minutes of either half in the league this season.
However, the opener was well worth the wait, as Alajbegovic scored his first Serie A goal in style by driving forward and unleashing a stunning strike that flew in off the far post.
It soon went from bad to worse for Allegri’s men, as defender Luca Marianucci was sent off for a second booking on his first Napoli start since September 2025.
The red card hampered the visitors’ ability to push for an equaliser, and Jeremie Boga secured the points three minutes from time with a brilliant strike of his own, as he cut inside and bent a shot inside Meret’s far post for his first goal of the season.
The victory sends Juve seventh in Serie A, one place above Napoli, while representing only their third win in the past 11 head-to-heads (D2, L6). While the pressure eases on Spalletti, it now ramps up on Allegri, whose side have still won just twice on their travels this term.
Flashscore Man of the Match: Kerim Alajbegovic (Juventus)