The Argentine Apertura championship ended in a three-way tie on Sunday as leading trio San Lorenzo, Boca Juniors and Tigre all won their final games to finish level on points at the top and force a playoff.
Goal difference is not used to decide the title and a three-way playoff will be held, the first in the tournament's history, with matches on December 17, 20 and 23.
All three teams won by single-goal margins on a tense afternoon to finish with 39 points from 19 games.
San Lorenzo won 1-0 at Argentinos Juniors, Tigre beat Banfield by the same score and Boca beat Colon 3-2 after racing into a three-goal lead in less than half an hour.
San Lorenzo struck the first blow of the day when Gonzalo Bergessio pounced on a loose clearance and smashed a shot past Sebastian Torrico in the eighth minute.
Argentinos dominated the rest of the first half but ran out of steam after the break and had Ignacio Canuto sent off for a second bookable offence in the 85th minute.
Boca went ahead in the ninth minute when Luciano Figueroa scored with a first-time shot from Fabian Vargas's cross and Juan Roman Riquelme added a second four minutes later, ending a quick exchange of passes by flicking the ball past Diego Pozo.
The game seemed over as a contest when Figueroa scored again in the 27th minute, scoring with his thigh from Jesus Datolo's cross.
But Colon fought back and reduced the arrears when Nicolas Torres scored with a left-foot shot from the edge of the penalty area three minutes before halftime.
After a 25-minute halftime break, which gave Boca the advantage of finishing around 10 minutes after their rivals, Lucas Valdermarin side-footed another goal in the 52nd minute after Javier Garcia failed to hold a cross.
Rank outsiders Tigre stayed in contention when playmaker Martin Morel scored his 13th goal of the tournament six minutes before halftime.
Defending champions River Plate finished bottom of the table after drawing their final game 1-1 with Estudiantes on Saturday.
River won only two games and managed a paltry 14 points in their campaign but did not go down as relegation is decided by average points over three seasons.