There was no margin for error for San Lorenzo on Tuesday evening after two defeats and a draw had left their Copa Libertadores already hanging by a thread. Diego Aguirre was said to be one defeat away from the sack so the stakes couldn’t have been higher when Universidad Católica came to the Nuevo Gasómetro.

The Chileans had denied San Lorenzo last week with a draw in Santiago and with minutes remaining, it appeared as though Fernando Cordero’s 77th-minute equaliser would do the same.

However, Aguirre threw on 18-year-old Nahuel Barrios for his debut, replacing the influential Fernando Belluschi, and a minute later the pint-sized teenager headed a dramatic winner. Quite how a player barely over five feet tall was able to get on the end of a cross in the six-yard box is a question for the Católica defence but the goal could prove vital in San Lorenzo’s bid to reach the knockout stages and Diego Aguirre’s job security.

Nicolás Blandi had capitalised on some earlier poor defending to volley Los Cuervos ahead but there was no doubting who the hero of the night was.

A little earlier and Atlético Tucumán also breathed life into their Copa Libertadores campaign with victory over Jorge Wilstermann.

After a goalless first half in which the Bolivian visitors should probably have led, El Decano forced an opener when Luis Rodriguez clipped the ball towards goal and afforded Ignacio Canuto the simplest of headed goals from under the crossbar.

David Barbona nodded in a second to ease the nerves but Luis Cabezas’ swift reply left work to do in order to hold on for the vital three points.

Pablo Lavallén’s side did just that and for the moment move up to third in Group Five but next week’s final home game against Peñarol is now of even greater importance.