The Serie A leader eased to a 2-0 win when the sides met in the league at the weekend, but found it a lot tougher to break down its opponent - 28 points worse off in the league - in the cup tie.

Zlatan Ibrahimovic squandered the best early opening on his first start since 22 November and Milan then dominated the second half, twice hitting the post and having a penalty shout turned down.

Neither side could find a way through in the additional 30 minutes, but it was the host which prevailed on spot-kicks to set up a tie with Fiorentina or Inter - Hakan Calhanoglu scoring the decisive penalty after Ciprian Tatarusanu had denied Tomas Rincon.