Boca Juniors head coach Diego Martinez stepped down after the club's 2-0 loss at Belgrano on Saturday, their third straight loss in Argentina's top-flight league.
The 35-time champions are 12th in the table with five wins in 16 matches. Boca have also crashed out of Cope de la Liga and Copa Sudamericana in penalty losses.
Martinez, who took over in January, told reporters that he had informed club president Juan Roman Riquelme about the resignation, thanking him for the opportunity.
Former Argentina and Barcelona midfielder Riquelme apologised to fans for the team's performance, with only one win in the last five league matches and a loss to rivals River Plate last weekend.
Boca host Argentinos Juniors next Sunday.