Edgardo Bauza's side, chasing their first ever Copa Libertadores title, took the lead after nine minutes through Ignacio Piatti, and, although Bruno Rodrigo headed Cruzeiro level in the 70th minute, San Lorenzo hung on for a 2-1 aggregate win. However, there was one blot on the night for the visitors as playmaker Leandro Romagnoli - only just back from a four-match ban - saw red 14 minutes from time after a fight, and left the pitch in tears.
"It was a very tough match," San Lorenzo midfielder Nestor Ortigoza told Fox Sports. "We knew it was going to be hard, but we marked them well and kept our focus. Cruzeiro did not have many opportunities despite their goal. We controlled the game. I think we deserved to progress."
Paraguayan side Nacional progressed to the last four for the first time in their history after a goalless draw with Argentina's Arsenal away from home was enough for a 1-0 aggregate victory.
Nacional midfielder Silvio Torales told Fox Sports: "We made a big effort. This is a draw with a taste of victory." We failed to profit from counter-attacks. Arsenal are technically good players, but we tried to do our best. I thank God for the gifts he is giving us."