The defender popped up in the last minute of extra time to win the game, after the Rossoblu had fought back from 2-0 down to snatch a draw after 90 minutes
Fredy Guarin and Rodrigo Palacio appeared to have assured qualification for the home side with a goal each, but Bologna battled back and regained parity through Alessandro Diamanti and Alberto Gilardino in the dying minutes of the second half. The game was finally decided thanks to Andrea Ranocchia, who scored the decisive strike seconds before the end of extra time.The quarter-final tie began in an even fashion, with Inter perhaps shading the opening exchanges, albeit facing strong resistance from an organised Rossoblu outfit. After failing to impress against Pescara at the weekend, Antonio Cassano was back to his best as he spearheaded his side's attack; the forward almost opened the scoring after a wonderful run through the heart of the away defence, only to drag his effort wide after running out of space in the penalty area.
The visitors struggled to break down their rivals in the final third, and looked most dangerous from distance. Alessandro Diamanti was a constant danger from range and fired an effort into the side-netting for his side's best early chance, while at the other end a delightful Cassano free kick was headed just wide by Matias Silvestre. Il Bambino's partnership with Fredy Guarin was giving the visiting backline no end of trouble, and it was no surprise when one of the duo opened the scoring.
Cassano laid off to his Colombian team-mate on the edge of the area with 34 minutes played, but Guarin still had a lot of work to do. With a delicate feint, the playmaker shrugged off his marker's attentions and released a bullet shot that left Federico Agliardi with no chance to save.
Bologna were left to chase the game from 1-0 down, but to their credit they refused to give up. Samir Handanovic made several top-class saves, denying Alberto Gilardino after the striker connected with Marco Motta's cross and keeping Diamanti at bay from distance once more. The goalkeeper's safe hands ensured Inter would enter the break with a slim advantage, as they chased a place in the last-four of Italy's domestic cup competition.
The visitors continued their search for an equaliser after the break, aided by a home side that re-emerged from the tunnel a far more defensive outfit than the first half. Bologna were gifted possession by the deep-lying hosts, but still looked most dangerous from distance, with another Diamanti effort whistling inches wide of Handanovic's post.
After an indifferent start to the half, Andrea Stramaccioni's side finally regained their rhythm and started to push forward again, inspired by Cassano who was directing proceedings. The speed of Alvaro Pereira almost yielded a second goal when the Uruguayan sprinted through to meet a deep pass, but he was thwarted by the swift reaction of Agliardi who came racing out to deny the wing-back one-on-one.
The match appeared to have ended as a contest 15 minutes from time, when Inter punished their opponents on the break. Juan's long pass upfield found substitute Rodrigo Palacio, and the Argentine did brilliantly to advance before curling a glorious 25-yard effort beyond Agliardi and into the top corner.
The game was not over yet though, as Diamanti hit back almost immediately with a free kick guided with expert precision into the roof of the net.
Andrea Ranocchia then gave his side a scare in heading against his own post, and there would be one more twist in the tale during regular time. Marco Motta floated a teasing centre across the Inter goal, and it was met by Gilardino who turned in to level the scores with just seven minutes remaining. The drama continued with Ranocchia bundling Cassano's cross into the net, but the effort was ruled out for a foul as the game entered extra time.
After that frenetic finish the game lowered in tempo during the next 30 minutes, although Javier Zanetti and Manolo Gabbiadini both missed golden chances to put their teams through. In the dying seconds, however, Ranocchia nodded home a corner to give his side the most dramatic of victories.
Inter move on to meet either Roma or Fiorentina in the last-four, with the two teams meeting on Thursday evening. Juventus and Lazio clash in the other semi-final tie.