A torrid week for River got worse when they were reduced to 10 men late in the first half, with Edwin Cardona breaking the deadlock from the resulting free kick to add insult to injury.
Cardona was shown a red card himself in the second half, though and River were soon level through Leonardo Ponzio's stunning long-range strike with just over 20 minutes remaining.
Parity lasted only four minutes, however, with Nahitan Nandez firing home the winner soon afterwards to lift them nine points clear at the top of the table after just eight games.
Find out how all of the action unfolded courtesy of Sports Mole's minute-by-minute coverage below.
This has been dubbed the biggest fixture in club football and the fiercest rivalry too, so we're expecting fireworks on this bonfire night.
Kickoff is at 9.05pm, which means that the team news should be filtering through any minute now...
People absolutely adore their football in Argentina, and the feeling is cranked up a few more notches any time these Buenos Aires rivals meet.
Boca will certainly be hoping that this one does go the way of the formbook, but River Plate have a point to prove and will be desperate to bounce back from the huge disappointment of throwing away a place in the Copa Libertadores final in midweek.
However, they conceded goal immediate before and after half time to let Lanus back into the tie and further goals from Acosta and Silva saw them throw it all away and lost 4-2 on the night, and 4-3 on aggregate.
Marcelo Gallardo's side have only won three of their opening seven matches so far this season, leaving them languishing down in 12 place heading into today's game.
Only three points separate Talleres Cordoba in second and Lanus in 14th, so a couple of victories for River would lift them right back into the top four, which are the Copa Libertadores qualifying positions.
River have scored only 11 goals at the other end too, so there are improvements to be made at both ends of the field if they harbour ambitions of catching Boca.
River's last league outing also ended in serve disappointment as they were beaten 4-0 by high-flying Talleres Cordoba, conceding three goals in the space of 12 second-half minutes en route to the heavy defeat.
Another defeat this evening, in addition to surrendering the bragging rights to Boca, would see River fall to three consecutive defeats for the first time since January.
River had made a strong start to the season with three wins from their opening three games, but they have now not tasted victory in the league since beating San Martin de San Juan on September 18.
Perhaps more importantly it would open up a 12-point gap to Boca which, even after this very early stage of the season, is a huge ask to make up on the defending champions.
Marcelo Gallardo's side are unbeaten in their 10 home outings across all competitions so far this season, winning seven of those and drawing three. River has also scored 30 goals in that time - an average of three per game which was significantly boosted by an 8-0 win over Bolivian side Wilstermann in the Copa Libertadores quarter-final.
Another draw, or defeat, tonight would mark the first time they have gone three home league games without a win since April, while they are also still looking for their first home league clean sheet of the season.
River still boast the all-time record for number of titles won, lifting the trophy 36 times in addition to finishing as runners-up on another 33 occasions. River's last title was back in 2014, though.
Tonight's visitors are already six points clear of their nearest challengers having won all seven of their matches so far, with only one other team even remaining unbeaten, yet alone failing to drop a single point.
Boca have the best attack in the division with 16 goals from their opening seven games - just shy of three per game - but arguably their most impressive attribute is their defending, with only one goal conceded in the league so far.
Should Boca prevent River from scoring this evening then it would be the second time already this season that Boca have strung together a run of four consecutive clean sheets.
That solitary setback did come away from home too, but they have won four of their five matches on the road, keeping clean sheets on either.
You have to go back to August 2016 for the last time Boca were beaten on the road in the Argentine league, and so far this season they have a 100% record of three wins from three without conceding.
Indeed, home and away their run of eight consecutive victories including the final of last season is their best since September 2006, more than 11 years ago, when they won 12 on the bounce.
Well, the headline news as far as River Plate are concerned is that Scocco starts having missed last weekend's drubbing, with the top scorer leading the line tonight. They missed him against Talleres Cordoba, but he returned in midfield and was quick to get back on the scoresheet - albeit from the penalty spot.
German Lux, who European football fans may remember from a stint at Mallorca and Deportivo La Coruna, starts between the sticks for the hosts.
There is another recognisable name in the shape of Rafael Borre on the bench, with the striker spending a year Villarreal last season.
Benedetto has scored eight league goals in seven appearances for the club so far this season and 34 in 40 outings overall for Boca, so if a chance falls his way tonight he is more than capable of snapping it up.
Cardona was on the scoresheet alongside two from Benedetto and an own goal, and he will lead the line again this evening.
This is a difficult one to call - the formbook screams an away win but that can often count for nothing in matches like these. I'm backing Boca to continue their perfect start to the season, but only just.
SPORTS MOLE SAYS: River Plate 1-2 Boca Juniors
The most recent of those came in May when River were two goals to the good inside 25 minutes en route to a 3-1 victory.
Boca's most recent visit came in December of last year when a certain Carlos Tevez was on the scoresheet twice as Boca came from behind in the second half to run out 4-2 winners.
RIVER PLATE STARTING XI: Lux; Montiel, Maidana, Pinola, Casco; Perez, Ponzio, Rojas; Fernandez, Martinez; Scocco
BOCA JUNIORS STARTING XI: Rossi; Jara, Goltz, Magalan, Fabra; Nandez, Barrios, Perez; Pavon, Benedetto, Cardona
The midfielder went for a bouncing ball which Cardona got to first, and then followed through with a karate kick that Eric Cantona and Patrice Evra would have been proud of, right into the chest of Cardona. The referee has no hesitation before producing the red card, and you can see why too. Terrible challenge.
It is a stunning strike from Cardona, though, with his free kick perfectly placed into the corner to leave Lux no chance in the River goal. Superb free kick.
It was a good, even match until River was reduced to 10 men, and Boca took the lead from the resulting free kick to add insult to injury. It looks like being a long way back for the home side now, and Boca will feel like they have the chance to get a big win against their fiercest rivals now.
In fairness to Fernandez it was a bouncing ball and he appeared to be making a genuine attempt to get it, but he followed through on the player and the referee was left with little choice but to produce a straight red.
Cardona actually went to the goalkeeper's side, but the strike was so good and so accurate that Luz was left with no chance. It really was a stunning strike, and one worthy of winning a game of this magnitude.
The first one was justified, but this one is a truly terrible decision by the referee, who must simply have been looking for a way to level things up again. The referee adjudges Cardona to have elbowed the man marking him, but there was barely any contact, and what contact there was with with his hand. Really poor decision, and one of the harshest red cards you will ever see.
This strike from Ponzio may well top the Cardona goal as he picks out the corner with a stunning 30-yard effort which leaves the keeper no chance. Brilliant goal from the veteran midfielder, and what a final 20 minutes we have in store now.
Boca looked to be on the ropes a bit, but now they are right back in the driving seat.
Technical issues meant that we could not bring you updates for the closing stages of the Superclasico, but the good news (if you're of a Boca Juniors persuasion) is that there were no further goals, so you didn't miss anything!
Boca hold on for a 2-1 win at the home of the biggest rivals, piling more misery on River Plate at the end of a devastating week for the hosts. The match saw nine yellow cards, two red cards and three goals of really high quality, but ultimately it is Boca who are celebrating.
Thank you very much for joining Sports Mole for tonight's match as Boca Juniors pile more misery on River Plate with a 2-1 win in the Superclasico. I will leave you with our match report, but from me it is goodbye for now!