Inter equalised with 20 minutes to go through a Romelu Lukaku penalty, and Eriksen's free-kick sunk the 10 men of AC Milan in the 95th minute.
Milan's surprise lead
The first half was cagey for the opening 20 minutes, but then Inter began to build a head of steam. They had a handful of clear chances, most of which fell to Lukaku. Alexis Saelemaekers and Diogo Dalot were struggling to contain Inter’s left-hand side.
On the half-hour mark, Milan took the lead completely against the run of play. A free-kick was recycled by Milan and Ibrahimovic worked a yard of space just inside the area and fired through the bodies into the bottom corner.
The first half ended in controversy. Lukaku was fouled by Alessio Romagnoli and suddenly the Belgian was incensed. In the melee, it seemed Ibrahimovic wound him up to the point of multiple players holding Lukaku back. The fracas carried on into the tunnel and the two picked up a yellow card each for their trouble.
Zlatan sees red
That feud carried over into the second half as Ibrahimovic was shown a second yellow card for a trip on Aleksandar Kolarov. With Milan down to 10 men, the pressure was relentless.
With 20 minutes to play, Rafael Leao tripped Nicolo Barella in the box but the ref wasn’t interested. The Inter players were furious and Achraf Hakimi took it upon himself to kick the ball out of play to force a decision. The referee headed over to the monitor and ultimately decided to award the penalty which Lukaku smashed in off the crossbar to make it 1-1.
Proceedings then took an unusual turn as the referee, Paolo Valeri, went off with a hamstring injury. After a long wait, the fourth official replaced him.
Milan barely created anything in the second half of the match whilst Inter spurned a series of half-chances. Late heroics from Ciprian Tatarusanu thwarted Lautaro Martinez and Lukaku as the match headed into 10 minutes of stoppage time.
Eriksen's killer blow
As the game entered the 96th minute, Eriksen expertly dispatched a free-kick from the edge of the box to win the game. It was the sort of set-piece fans have wanted to see more of from the Dane since he joined Inter. It could be a fitting parting gift as he’s continuously linked with a move away.
This cup tie seemed to be a chance for both Milan sides to showcase their squad depth, something that will be so key to the ongoing title race. On paper, at least, Inter have won that battle.
In the semifinal Antonio Conte's side will face the winner of Juventus vs SPAL, which will be played tomorrow night.