The midfielder's scrambled goal came from a quick break after the Boca defence had blocked a shot at the other end from River captain David Trezeguet, who was attempting to mark his first big Buenos Aires derby with a goal on Sunday.
"The goal is important because of the difficult times Boca is having," Erviti said, referring to his team's poor form with only three points from their last five matches.
A packed Monumental was treated to plenty of excitement but only glimpses of good football.
River shocked Boca by scoring from a first-minute free-kick and added a superb second goal before Boca hit back twice in the last 15 minutes.
Midfielder Leonardo Ponzio repeated his trick of River's previous home match when he hit a right-footed free-kick from 30 metres out on the left inside the near post with goalkeeper Agustin Orion reacting too late.
Uruguayan striker Rodrigo Mora, a thorn in the side of Boca's defence, put River two up in the 70th minute with a superb shot from a tight angle on the right.
But five minutes later substitute defender Leandro Gonzalez Pirez gave away a penalty converted by Boca's Uruguayan striker Santiago Silva.
River had been forced to make two substitutions in the first half after defender Ramiro Funes Mori and midfielder Martin Aguirre both suffered knee ligament damage.
The referee delayed the start of the second half for several minutes until River fans had removed a giant inflatable pig in Boca colours they had paraded at halftime.
Boca have 19 points from 12 matches, three more points than River, who hosted the first competitive derby against their arch-rivals in 17 months following their relegation in June 2011.
Newell's Old Boys top the table with 26 points after Saturday's 2-1 home win over title holders Arsenal in Rosario, where striker Ignacio Scocco scored twice including a brilliant overhead goal.
Newell's were a man short for 30 minutes after former Argentina defender Gabriel Heinze was sent off for a second booking.
Velez Sarsfield, who beat Racing Club 1-0, are second with 23 points. Belgrano are third with 22 points after a 1-0 home win over Union in Cordoba and Racing fourth with 21.
- Sports & Recreation