San Lorenzo won the first half of the Argentine first-division season Sunday after a 0-0 draw with Velez Sarsfield, thanks to previous champion Newell's Old Boys earning only one point in a 2-2 draw against Lanus.
San Lorenzo finished with 33 points after 19 matches, two ahead of Lanus, Velez and Newell's Old Boys, any one of which could've taken the title with a victory on the last day of the season.
Like many Latin American countries, Argentina divides its season into two halves and crowns champions for each.
Goalkeeper Sebastian Torrico was the hero for San Lorenzo after he tipped over a fierce volley from Agustin Allione in the last minute of the game, with Velez searching for a title-winning goal.
Velez made a bright start and had the greater possession but San Lorenzo had more opportunities, coming close in the 10th minute when Ignacio Piatti weaved through the midfield and was brought down on the edge of the box, but the resulting free kick was deflected over the crossbar.
TV replays showed San Lorenzo should've had a penalty when Fernando Tobio clearly tugged at Santiago Gentiletti's shirt three minutes before half time.
Velez pushed forward in the last 30 minutes of the game and almost scored when Allione's curled shot from the edge of the area struck the left post, with Torrico beaten.
San Lorenzo - one of Argentina's "big five" teams - won its 12th title of the professional era, with the start of the game suspended for 30 minutes due to legal problems in opening the stadium, which were resolved 90 minutes before the game was due to start.
Newell's opened the scoring in the 53th minute through Pablo Perez, before Paolo Goltz headed in to level the scores two minutes later.
Lanus' Carlos Izquierdoz conceded an own goal to put Newell's back into the lead, but Jorge Pereyra equalized for Copa Sudamericana holders Lanus in the 74th.
