Lautaro Martinez starred for Inter as his double helped Antonio Conte's side to a 2-1 victory over SPAL and moved the Nerazzurri top of Serie A.
With Juventus having drawn with Sassuolo in Sunday's early fixture, Inter knew a win at San Siro would be enough to leapfrog Maurizio Sarri's men, and they had too much for a struggling SPAL side who are now winless in seven matches.
Martinez spearheaded Inter's attack – picking out the bottom-left corner of Etrit Berisha's goal with supreme accuracy in the 16th minute before doubling his tally with a well-placed header prior to half-time.
Mattia Valoti struck to spark a rejuvenated SPAL performance after the break, yet – despite Martinez squandering two golden chances to round off a hat-trick – Inter held firm to claim top spot.
Romelu Lukaku broke through SPAL's line in the 11th minute, though Berisha did well to rush out and close the angle.
Berisha was beaten five minutes later, however – Martinez gliding forward before directing a low finish across SPAL's goalkeeper.
Lukaku and Marcelo Brozovic both went close as Inter kept up the pressure, but the hosts had their second four minutes before the break, Martinez guiding home Antonio Candreva's excellent first-time cross.
Against the run of play, SPAL pulled themselves back into contention early in the second half as Valoti carved through Inter's defence and slotted in off the left-hand upright.
Alessandro Murgia might have made it 2-2 had he connected well with a looped cross, while Martinez saw a close-range header saved by Berisha before he then failed to beat the goalkeeper when one-on-one soon after.
Matias Vecino's close-range miss buoyed SPAL's resolve, but Andrea Petagna failed to take advantage when the visitors' next chance came his way, while Jasmin Kurtic went close with a rasping long-range strike as Inter held onto the points.
What does it mean? Nerazzurri make most of Juventus off-day
Juve have long dominated Serie A, but in the form of Conte's Inter, the Old Lady seem to have serious title rivals this season.
Inter – now top by one point – have won 12 of their opening 14 Serie A matches in a season for the first time, while they have also become the fifth side to find the net in each of their first 14 league matches of a campaign in the 21st century, after Juve, Milan, Fiorentina and Roma.
In-form Martinez strikes early... again
Martinez needed no second invitation to open the scoring, though it is perhaps no surprise given his record of scoring early goals in Serie A this season. Overall, six of the striker's eight league strikes have come in drilling in the opening 30 minutes.
Sluggish second-half start a cause for concern
Inter were in cruise control heading into the break, but a stuttering start to the second half enabled SPAL to wrest their way back into the contest and, had the visitors possessed more quality in attack, Conte's team could easily have been made to pay.
Inter welcome Roma to San Siro on Friday in Serie A, while SPAL's next outing comes against Lecce in the Coppa Italia on Wednesday.