AC Milan will stay top of Serie A this weekend after Saturday's tight 1-0 win over Empoli moved them five points clear of the chasing pack.
Juve were 14 points off the pace and languishing seventh in the table in December, but have revived their slim hopes of winning a 10th title in 11 seasons.
Milan Djuric headed Salernitana in front on 72 minutes before Milan salvaged a point thanks to a long-range effort by Ante Rebic five minutes later.
Stefano Sensi crashed the hosts back ahead with a powerful drive in the 104th minute which finally settled the match in Inter's favour.
Stefano Pioli's side stayed four points behind city rivals and league leaders Inter Milan, who were 1-0 winners over Torino
Napoli have 24 points, two more than AC Milan, after equalling the best start in club history, having also won their first eight games in 2017-18.
Juve missed a cutting edge in front of goal in what was the worst possible start to life without the 36-year-old, who last term topped the Serie A goals charts and scored over 100 times for the in three seasons in Italy.
Financial problems led to coach Antonio Conte's departure and the sale of star players Romelu Lukaku and Achraf Hakimi, but they played as though their troubles were behind them under new boss Inzaghi.
Serie A: Napoli run riot against AS Roma to pull clear of Inter Milan; Juventus close in on title with Empoli win
Napoli ran riot in Rome on Sunday with a 4-1 victory which pushed Roma out of the European places and consolidated second place for Carlo Ancelotti's side in Serie A ahead of Inter Milan who fell 1-0 at home against Lazio
Serie A: Juventus edge past Empoli thanks to Moise Kean's winner; AC Milan go down to Sampdoria to suffer second straight defeat
Rising teenage star Moise Kean stepped up in the absence of Cristiano Ronaldo to rescue a 1-0 win for Juventus against lowly Empoli on Saturday as the champions opened up an 18-point lead at the top of Serie A.
Serie A: Relegation-threatened Empoli fire coach Giuseppe Iachini, rehire former boss Aurelio Andreazzoli
Iachini replaced Andreazzoli in November after Empoli won only one of 11 matches in Serie A under the 65-year-old coach, who had led the Tuscan team to the Serie B title and direct promotion last season
Serie A: Striker Krzysztof Piatek scores again as AC Milan keep Champions League ambitions on track with win over Empoli
Trigger happy Polish striker Krzysztof Piatek continued his goal-scoring spree in a 3-0 win for his new club AC Milan over lowly Empoli on Friday to keep their Champions League ambitions firmly on track.
The club have given no further details of the reasons behind Nainggolan's suspension but according to the Italian press, the action has been sparked by the 30-year-old's habit of turning up late for training.
Serie A: Dries Mertens scores hat-trick as second-placed Napoli thrash Empoli 5-1 to put pressure on leaders Juventus
Dries Mertens scored a hat-trick as Napoli warmed up for next week's crucial Champions League game against Paris Saint-Germain with a 5-1 thrashing of Empoli to go back to second place in Serie A and put the pressure on champions Juventus
Serie A: Argentine striker Mauro Icardi's brace takes Inter Milan into second place after Lazio thumping
Inter Milan captain Mauro Icardi scored twice as his team beat Lazio by a scoreline of 3-0 to go second in the Serie A table, behind league leaders Juventus.
Serie A: Cristiano Ronaldo's second-half brace helps Juventus battle past Empoli and take seven-point lead
Cristiano Ronaldo struck twice, including a thunderous 25-yard drive, as Italian champions Juventus surged seven points clear in Serie A following a battling win at Empoli.
Serie A: AC Milan's stuttering start to season continues after being held by Empoli; Sassuolo ease past SPAL
AC Milan's stuttering start to the season continued on Thursday when the former European champions were held to a 1-1 draw at Empoli for a third successive Serie A stalemate
Serie A: Inter Milan squander two-goal lead to draw against Torino; Genoa beat Empoli in emotionally-charged match
Inter Milan — who returned to the Champions League after finishing fourth in Serie A last season — had fallen to a shock 1-0 opening defeat to Sassuolo.
Maurizio Sarri, named as new Chelsea manager, is owner Roman Abramovich's latest gamble in quest for 'perfect football'
Appointing Maurizio Sarri, the banker who turned into a football coach to help Empoli and Napoli scale new heights in the Italian leagues, is Abramovic's latest attempt at bringing attractive football to Stamford Bridge.
Premier League: Antonio Conte to be sacked as Chelsea manager; Maurizio Sarri will be likely replacement, say reports
Sarri, a former banker, has been linked with the post even before the 59-year-old stepped down from the Napoli hotseat after guiding them to runners-up spot behind Juventus for the second time in three campaigns.