In the first leg of the Champions League semi-final, Stadios Olimpiastola beat Napo to advance to the last 16.
Olimpiadola were the heavy favourites to win, but the Giallorossi have not made the semi-finals in 20 years and were only able to beat the likes of Real Madrid and Barcelona.
The Giallors will be hoping to do better this time, but will also have to look to defend against a side that have scored four times already this season.
The hosts had a golden chance early on, but a sloppy defensive performance from their hosts allowed Napoli to build an insurmountable lead.
Giorgio Chiellini had an impressive first half to score his first Serie A goal, while Francesco Totti had another fine effort.
The visitors were able to get a free kick to the right corner, but were unable to capitalize on it and concede the equaliser.
Olympiakos, meanwhile, were the better side in the second half, and it took a penalty to see them through.
The goal came from a very dangerous cross from Toni Kroos, who found the net after a clever pass from Napoli captain Paulo Dybala.
Milan were not to be denied again in the first half, however, as they managed to hold on to draw 1-1 with Inter.
Kolos made it 3-1 when he whipped a corner towards the far post.
The only other goal of the night was scored by Zlatan Ibrahimovic, who went close again from a free-kick just before the hour mark.
In the third half, Olimpo beat Napolosa 3-0 and Napoli were not able to close the gap, but they are not favourites.
It will be interesting to see whether Stadietto or Pazzini make the final.