Riestra topped the group with 22 points from 10 matches, while River, who lost to Palmeiras in the Copa Libertadores quarter-finals during the week, is second on 18 points.

The visitors stunned River in the 12th minute when Alonso rose highest to meet Pablo Monje’s corner and head home the opener in Buenos Aires.

River responded in the 25th minute through Giuliano Galoppo, who fired a powerful right-footed shot past Riestra goalkeeper Ignacio Arce.

Riestra restored their lead early in the second half when Ramirez showed composure inside the box to place his shot beyond River keeper Franco Armani to make it 2-1.

River’s hopes of a comeback were dashed when forward Maximiliano Salas was sent off for dissent towards an assistant referee in the 81st minute, as the hosts slumped to a fourth consecutive defeat in all competitions.

“The first thing I want to do is apologise to our fans, because we are not going through a good moment,” River manager Marcelo Gallardo said.

“In this short week, we had four games with negative results, so they deserve an apology.

“It wasn’t the moment we wanted to be in, and yet they are always there for us. We couldn’t turn the page on the Copa Libertadores and give them a victory today.

“I take responsibility for the team’s current form. We’ve tried different things, we’ve given players opportunities, but we haven’t been able to get things flowing. It’s my responsibility and I accept that,” he added.