Inter started off well when 17-year-old Ibrahima Mbaye completed a give-and-go with Wesley Sneijder to burst to the by-line and pull back past the goalkeeper, but some desperate defending stopped Milito tapping in.
Then a great run from Javier Zanetti resulted in the ball being pulled back for Coutinho, whose deflected finish came off the underside of the crossbar from six yards.
Bu then after 25 minutes, Hajduk got back in the game when Samuel completely mistimed his tackle to take down Vukovic in the penalty box and Ante Vukusic sent Samir Handanovic the wrong way from the spot.
Surprisingly Inter were still playing a wide open game and both sides could have scored in the first half. First Antonio Milic burst through between defenders and forced Handanovic to rush off his line to parry for a corner.
Then Coutinho should’ve equalised when he was sent clear through the centre by Sneijder, but drew out the goalkeeper and toe-poked it wide of the far post.
Inter’s defensive frailty came back to hurt the team again in the 58th minute when Hajduk scored with a classic counter-attack as Vukovic scored a terrific goal from just inside the box.
This made it 3-2 on aggregate for Inter, so one more goal from the visitors would force extra time.
Inter continued to attack with Sneijder and Ranocchia both going close before Blazevic performed a fine double save on the Longo cross and Sneijder’s follow-up.
Longo sprung the offside trap on Guarin’s through ball, but Blazevic timed his run perfectly to close down the youngster. Defender Matias Silvestre replaced the tired Sneijder for the final seven minutes, as Inter clung to their slender 3-2 aggregate lead in front of mostly silent fans.