Milan came into this clash still reeling from surrendering top spot in Serie A at the weekend, but they channelled that frustration by taking a fourth-minute lead through Samuele Ricci.
Honest Ahanor could only partially clear a Milan corner into the midfielder’s path, and his shot took a hefty deflection off Ederson before flying in.
However, La Dea’s response was encouraging, with Isak Hien and Davide Zappacosta both having chances to restore parity before Ahanor agonisingly blazed over the bar from close range after being spotted by Mario Pasalic.
It was the Nigerian international’s first goal of the season, and left the contest finely poised heading into the second period.
The Rossoneri played with more intensity after the break, helped by the introduction of Christopher Nkunku and Ruben Loftus-Cheek – the latter replacing the injured Santiago Gimenez.
The Frenchman almost made a quick impact, as he played an enticing ball into the box that was headed back towards goal by Davide Bartesaghi before Youssouf Fofana fired wide from close range.
Both sides laboured in their respective pursuits of all three points, epitomised when Hein’s lacklustre header drifted wide from Marco Brescianini’s corner. Zappacosta looked to change that narrative when he cut inside from the left and unleashed a right-footed drive towards goal that was superbly parried to safety by Mike Maignan.
Ultimately, there would be no winner in a result which will leave Massimiliano Allegri arguably the happier of the two managers. His Rossoneri side are now unbeaten in nine matches across all competitions (W6, D3), while counterpart Ivan Jurić was left to bemoan another two dropped points here in Bergamo.
The Croatian is yet to taste victory against Allegri after 10 meetings (D4, L6), but more crucially, has seen his team win just three of their previous 16 home league games in what has been a peculiar start to the campaign.
Flashscore Man of the Match: Mario Pasalic (Atalanta)