Inter captain Mauro Icardi had a woeful night in front of goal as the Milan derby ended goalless.
The Argentinian striker, who scored a hat-trick in the return fixture, missed two open goals and had an effort ruled out for offside by the Video Assistant Referee – but the draw was enough to dent their rivals’ Champions League hopes.
Gennaro Gattuso’s Milan, the hosts at San Siro, went into the game eight points behind their city rivals, who hold the final top-four spot.
But they have Icardi to thank for the gap not being even larger with eight games left to play in Serie A.
Icardi had shown fine composure in the first half to collect Antonio Candreva’s pass and fire under Gianluigi Donnarumma, but after the celebrations had finished the goal was ruled out for offside.
But his finishing touch deserted him in the second half. First he somehow scuffed a shot wide from inside the six-yard box after Candreva had squared the ball to him.
And then in stoppage time, Joao Cancelo’s cross from the right found Icardi, who fired wide sliding in at the far post.
AC Milan paid tribute before kick-off to former midfielder Ray Wilkins, who died on Wednesday aged 61. Franco Baresi, a former team-mate, laid a wreath behind one of the goals before holding up a club shirt with ‘Wilkins 8’ on the back.
Claud Adjapong saw red after 27 minutes, after input from VAR, for a foul on goalkeeper Stefano Sorrentino.
The visitors held on until the 72nd minute when loanee Emanuele Giaccherini found the bottom right corner from close range.
Skipper Francesco Magnanelli then received a second yellow card with seven minutes left – but Sassuolo hit back when Francesco Cassata’s inswinging free-kick from near the halfway line bounced near the penalty spot and then flew into the top right corner of the net.
Both teams sit on 29 points, five clear of the bottom three.
Hellas Verona’s survival hopes received a major blow as they were beaten 3-0 by bottom club Benevento.
Gaetano Letizia gave the hosts a 25th-minute lead before Cheick Diabate’s second-half brace secured Benevento’s fourth win of the campaign – and first by more than a one-goal margin.
Verona are four points from safety, while their conquerors are nine points further back.
Crotone remain two points ahead of Verona after they were thrashed 4-1 at Torino.
Andrea Belotti scored a hat-trick, having previously scored just six league goals this season, while Iago Falque was also on target as Torino ended a four-match losing run.
Davide Faraoni pulled one back late on for the visitors, who have won only one of their last nine league games.