The hosts have won all four home matches in the second phase so far, but they face a side they have only beaten once in eight attempts on their own ground.
Match preview
After suffering their first league defeat against Racing Club, Union swiftly bounced back with a 1-0 victory over Rosario Central at the Estadio 15 de Abril last Wednesday, thanks to Mauro Pitton's 70th-minute goal.
Kily Gonzalez will be hoping his side can embark on another winning run in the league, having gone unbeaten in their opening six games of the new Primera Division campaign, claiming four wins and two draws while scoring seven goals and keeping four clean sheets.
Tatengue remained second in the Primera Division table with 17 points from eight matches, one point behind league leaders Huracan.
Union will aim to maintain their position or, ideally, climb to the top if results go in their favour, but they must first overcome the hurdle of River Plate, a team they have only beaten once at home in eight tries.
However, the hosts will draw confidence from their home form this season heading into Sunday's clash, as they have won each of their four games at the Estadio 15 de Abril, scoring six goals and conceding just once.
Defending champions, River Plate, ended a three-match winless streak with a 1-0 victory over Sarmiento at the Estadio Monumental last Sunday, courtesy of a late strike from 16-year-old midfielder Franco Mastantuono.
Los Millonarios have endured a difficult start to the second phase of the Argentine Primera Division, currently occupying ninth position with 13 points, level with 10th-placed Atletico Tucuman.
Martin Demichelis's side remain five points off the summit but will be hoping to embark on a strong run to close the gap as soon as possible.
The record league champions have the opportunity to win two league games in a row for the first time since the opening two matches, while they can also secure a third consecutive victory against the hosts.
However, their away record in the current campaign leaves much to be desired, as they have lost all three matches on the road, scoring just once and conceding five.
Union Argentine Primera Division form:
W
W
W
D
L
W
River Plate Argentine Primera Division form:
L
W
L
D
L
W
River Plate form (all competitions):
L
D
W
D
L
W
Team News
Union will head into this clash without any suspension or injury worries, leaving the manager with a wealth of options.
Adrian Balboa and Nicolas Orsini have been the preferred duo in attack for the last couple of matches, and we expect them to start together once again.
River Plate are set to remain without the services of Gonzalo Martinez, who has been out with a cruciate ligament tear since January.
Agustin Sant'Anna picked up a knee injury in early July, and he is expected to remain sidelined until late August.
Attacking midfielder Claudio Echeverri is away with the Argentine Olympic team and is unavailable for the next couple of weeks.
Union possible starting lineup:
Cardozo; Torren, Pardo, Paz; Vargas, Rivero, M. Pitton, Mosqueira, B. Pitton; Orsini, Balboa
River Plate possible starting lineup:
Armani; Casco, Pirez, P. Diaz, E. Diaz; Kranevitter; Simon, Mastantuono, Lanzini; Solari, Borja
We say: Union 1-0 River Plate
Union have been absolutely superb on home soil in this campaign, with a perfect record so far, while scoring six times and conceding just once.