Milan needed an Olivier Giroud header to force extra time, eventually beating Genoa with a Rafael Leao misplaced cross and Alexis Saelemaekers to reach the Coppa Italia quarter-final.
The winners will face either Lazio or Udinese next month.
Both sides were decimated by injuries, COVID and Africa Cup of Nations duty, as the hosts missed Zlatan Ibrahimovic, Davide Calabria, Simon Kjaer, Alessio Romagnoli, Samu Castillejo, Pietro Pellegri, Franck Kessie, Fode Ballo-Toure and Ismael Bennacer, but Ante Rebic and Fikayo Tomori returned. There were reports it will be Andriy Shevchenko’s final Genoa game regardless, just two months after taking the job. January signing Kelvin Yeboah was thrown straight in for his debut.
Daniel Maldini rode two tackles before his shot was blocked by Ostigard and from the resulting corner Rade Krunic’s header clipped the top of the crossbar.
However, Zinho Vanheusden surged forward and everyone backed off, his strike palmed one-handed around the post by Mike Maignan at full stretch. On the resulting corner, January signing Leo Ostigard was allowed a free header to give Genoa the lead, as Theo Hernandez lost his man.
Things got worse for Milan, as Tomori then limped off with a left knee issue, then Yeboah nodded over from another dangerous corner.
It should’ve been 2-0, Manolo Portanova only hitting the side-netting from close range after Caleb Ekuban pulled back from the by-line.
Another promising Ekuban run wasn’t finished off after the restart, while Adrian Semper had to make a tricky save from point-blank range on Matteo Gabbia after Giroud knocked down a free kick.
Johan Vasquez deflected another Giroud attempt wide, but Milan finally got their equaliser when Theo Hernandez whipped in a no-look cross from the left and Giroud’s towering header steered it back across the face of goal into the far top corner.
The momentum shifted and Giroud nodded wide from a Rafael Leao cross, while Florenzi’s rocket was straight at Semper and Ostigard needed a desperate block on Leao.
It was 1-1 and went to extra time. Leao nutmegged Ostigard with his finish, but Semper got a fingertip to push it inches past the far post.
Sandro Tonali unleashed a rocket that bent outwards at the last second to skim the upright, but it took a moment of good fortune for Milan to take the lead.
Leao clearly intended to cross from the left, but he mis-kicked it and the ball floated over Semper into the far top corner. The Portuguese forward didn’t even try to disguise it was a mistake, laughing sheepishly as it went in.
Genoa fought back, Ostigard blasting just over the bar, as did Brahim Diaz on an Alexis Saelemaekers lay-off, while Paolo Ghiglione tested Maignan at the near post.
Theo Hernandez provided another assist, sprinting down the left and pulling back for Saelemaekers to finish it off from 12 yards.
Milan 3-1 Genoa aet
Ostigard 17 (G), Giroud 73 (M), Leao 102 (M), Saelemaekers 112 (M)