Sassuolo held visitors Milan to a 1-1 draw on Sunday evening in the sixth round of the Italian league, denying coach Ruben Amorim the chance to take his side up to third place in Serie A.
Adrien Rabiot put Milan ahead on 63 minutes. Five minutes later Odenthal levelled for Sassuolo, and the two sides ended up sharing the points.
Milan climb to 12 points in fourth as a result, while Sassuolo sit on eight in tenth.
Repeated stoppages for injuries disrupted the first half, which ended goalless despite attempts from both sides. Sassuolo were the livelier in the opening minutes. Milan needed time to assert their control of the ball.
On 18 minutes, Matteo Gabbia suffered an injury that forced him off the pitch on a stretcher, with Koni De Winter replacing him two minutes later. Six minutes after that, Sassuolo made an early change of their own as Fedi Lessen went off injured and Kass Odenthal came on.
Rabiot nearly broke the deadlock on 32 minutes, heading over the bar. Sassuolo goalkeeper Arijanet Muric then shone before the break, keeping out two dangerous efforts from Gonzalo Ramos and clearing a Strahinja Pavlovic header in stoppage time.
Amorim turned to Luka Modric at the start of the second half, taking off Pervis Estupinan in a bid to energise the midfield.
More Milan pressure followed, and the breakthrough arrived on 63 minutes. Modric slipped the ball to Rabiot, who lashed it from a tight angle inside the penalty area into the roof of the net.
The visitors' joy lasted five minutes. Odenthal took the match back to square one on 68 minutes, following up after a corner from Armand Lauriente and a touch from Josh Doig sent the ball his way, firing home from close range amid the crowd of bodies.
Chances came at both ends after the equaliser. Domenico Berardi blazed one over the bar, and Mike Maignan kept out two dangerous Sassuolo efforts on 65 minutes.
Sassuolo thought they had a winner on 88 minutes, only for the referee to blow for infringements inside the penalty area and rule it out. Nothing changed in the remaining minutes before the final whistle.