Carlos Tevez scored his first goal for Boca Juniors at La Bombonera in more than a decade but it was not enough to prevent his side from crashing to a shock 4-3 defeat to Union in the Argentine championship on Sunday.
Boca took an early lead through Jonathan Calleri but the home side began to unravel when goalkeeper Agustin Orion brought down Union striker Lucas Gamba with a dangerous tackle inside the box and was sent off in the 27th minute.
Victor Malcorra equalised with the penalty and the visitors from Santa Fe then took the lead five minutes later through midfielder Mauricio Martinez.
Tevez brought Boca level a minute into the second half but Union defender Emanuel Britez restored their lead in the 65th minute.
Calleri looked to have salvaged a point for the home side two minutes from time, shortly after Boca coach Rodolfo Arruabarrena had been sent to the stands for dissent.
However, Gamba scored with a header in stoppage time to hand Union the 4-3 win and all three points.
“It was a match in which we scored a quick goal and then had chances to get the second and go in at the break with a comfy lead but it’s unbelievable the errors we had,” Tevez said.
“There must be a reason for a result like that. Boca didn’t play a good match,” added Tevez, who is back at his first club after a decade in Brazil, England and Italy.
The defeat saw Boca fall into a share of the league lead, on 40 points from 19 matches, with San Lorenzo, who beat Gimnasia 1-0 on Saturday. Goal difference is not taken into account.
River Plate are second on 37 points with a game in hand. Their visit to Defensa y Justicia was postponed while they prepare for the second leg of the Libertadores Cup final at home to Tigres of Mexico on Wednesday.