A weakened Racing side held out to pick up their first victory in the newly-named Copa Diego Maradona 1-0 at home to Unión.
The Estadio Juan Domingo Perón side are already out of the competition, having lost the rest of the games in their group, and with a midweek Copa Libertadores outing against Flamengo coming up, there were a number of changes.
Unión started brightly as striker Fernando Márquez went close with a near-post header direct from a corner in the 10th minute. However, much of the early play was contested in the middle of the park in a scrappy opening phase.
From then on Racing dominated much of the first half. The highly promising Carlos Alcaraz looked to provide an opening with a burst of pace past Lucas Esquivel, though the final ball left a lot to be desired.
Alcaraz was a real threat in the first half, feeding through Walter Montoya only for him to place the shot straight at Bonansea in the Unión goal.
The first half looked like it would fade into obscurity until a superb early low cross from Montoya found Alcaraz in acres of space. A cool first time finish into the bottom right corner was enough to give Racing a deserved 1-0 lead heading into the break.
Unión made a double switch upfront at half time as Javier Cabrera and Martínez were replaced by Mauro Luna Diale and Gastón González in search of an improved second half.
It almost made an immediate impact as González fed Kevin Zenon into a goal scoring position on the edge of the 18 yard box with a vital block from Fernando Prado stopping a certain shot on target.
Racing went straight up the other end and, after a scramble in the box following a blocked free kick, Caceres found himself with space to find a shot towards the bottom right corner which was well saved. An unintentional elbow from that set piece left a bloodied Alcaraz needing treatment.
The end to end, open second half provided a complete contrast to the play in the first with Unión coming into the game. Racing manager Sebastian Beccacece looked to stem the tide replacing Angel Gómez with Evelio Cardozo.
Though only Matias Ibañez could stop a sure goal after Franco Calderon’s header from a corner on the hour mark.
Racing were able to ride the pressure from Unión and pushed for a second, with Lucas Orban’s free header at the far post creeping inches wide of the target with 20 minutes to play.
Unión made another double change looking to find a way back into the game to keep close tabs with group leaders Atlético Tucumán bringing Gaston Comas and Juan Portillo into the frey.
And they came close through another Calderon header that fell straight into the waiting arms of Ibañez.
Man of the match Walter Montoya posed a real threat from set pieces, before being replaced by Mauro Luque, providing yet another good chance for Orban who fluffed his lines heading wide again with ten minutes to play.
Unión pushed for an equaliser as the minutes ran down with a number of wasted set pieces. Substitute Gonzalez was lucky to stay on the field after a frustration-ridden rough challenge as added time ticked away.
And in the last chance of the game, a poor clearance from a Unión ball across the face left Gaston Comas with the goal in his wake, only to clear the bar with his effort.
A hard earned victory for a Racing reserve side that road its luck at times but showed real quality in their winning goal. Union will see this as a chance missed against a weakened opposition.