Peruvian Primera Division Review: Juan Aurich close on Apertura title
Barring a final-day catastrophe, Roberto Mosquera's men will lift the title as they sit three points clear of the table - and substantial goal difference - from second-placed Melgar.
The winners of the Apertura face the Clausura champions in a play-off for the overall championship.
Juan Aurich won 2-1 away at Universidad San Martin, with the hosts finishing the game with nine men.
The match started well for San Martin, Santiago Silva putting them ahead in the 21st minute after a defensive calamity from Juan Aurich.
San Martin went down to 10 men after a rash challenge from Johnnier Montano, and four minutes later Edgar Balbuena netted a penalty - awarded for an apparent handball.
Osmar Noronha then scored the all-important winner with 12 minutes to play, tapping in a cross to seal the three points.
San Martin went down to nine in injury time, when Jack Safra earned a straight red.
Melgar failed to win for a second match in succession, as their bid to top the table all but ended when they were held 2-2 at home to Sport Huancayo.
Juan Reynoso's men came from behind to lead 2-1 via a Minzun Quina penalty and a Bernardo Cuesta effort, but Kleyr equalised on the stroke of half-time for Sport.
The equation for Melgar to top the table is unlikely - they must win at Alianza Lima on the final day, hope Juan Aurich lose at home to Universitario, and inflict a nine-goal turnaround in differential to the leaders.
Universitario would have been playing for their title ambitions, but they fell to a 2-1 home loss to Leon de Huanuco.
Gianfranco Espinoza and Diego Manicero both struck seven minutes apart, before Cris Martinez scored late - only for it to be rendered consolation for Universitario.
Inti Gas snapped a three-match losing streak, but were held to a 3-3 draw at home to Cesar Vallejo.
A Francesco Recalde brace had Inti Gas well clear at the half-hour mark, only for Cesar to claim the lead with 12 minutes to play.
Marcos Jaunarena, Jeremy Rostaing and Daniel Chavez all scored to put the visitors in front, before a Carlos Orejuela penalty spared Inti Gas a fourth straight loss.
Union Comercio enjoyed a 2-0 win at home to Sporting Cristal, to move to 21 points and above Cesar Vallejo into fifth.
Mid-table Real Garcilaso thrashed San Simon 4-1, Victor Ferreira bagging a brace for the winners.
Alianza Lima are unbeaten in four, and climbed above UTC Cajamarca with a 2-0 win over them.
Bottom club Los Caimanes won just their third match of the phase, coming from behind to pip Cienciano 2-1.
Roberto Jimenez scored a double, the second of which in the 87th minute sealed a thrilling victory for the strugglers.