Ariel Garcia's 54th-minute strike was enough to guarantee Gimnasia their second straight league victory, despite playing the last 11 minutes with just 10 men after Matias Melluso's second yellow card.
The result left Gimnasia 19th in the 24-team Argentinian Superliga standings with one match remaining in the season. They now have six wins, four draws and seven losses since Maradona was appointed manager in September.
Under Argentinian football's promotion-relegation system, teams are measured on their average number of points over the past three seasons.
Gimnasia's fate is likely to hinge on the result of their final match of the campaign at Boca Juniors next Sunday. The clash at La Bombonera - Maradona's former temple - could also decide the title as second-placed Boca attempt to usurp rivals River Plate, who drew 1-1 at home to Defensa y Justicia on Saturday.
"I love Boca, but I'm the manager of Gimnasia y Esgrima," 1986 World Cup winner Maradona told reporters after being asked about the upcoming duel with his former club.
On Friday, Boca secured their fifth straight Superliga win by thrashing Colon Santa Fe 4-0 away from home.