APR went into Saturday’s game at Amahoro National Stadium six points clear at the top, but saw their lead reduced to three points after tasting their third defeat this term.
Sarpong scored from the spot in stoppage time to seal victory for Rayon after Emmanuel Imanishimwe brought down Gilbert Mugisha in the penalty area.
It was Sarpong’s 11th league goal for the Blues, and the Ghana-born striker trails joint leading scorers; Jules Ulimwengu (Rayon) and Djuma Nizeyimana (SC Kiyovu) by just one goal.
Mugisha came off the bench with seven minutes to clock, replacing Eric ‘Radu’ Iradukunda who was noticeably exhausted.
The military side, APR, started the game with a lot of pressing, and could have earned an early lead through Fitina Omborenga and Muhadjiri Hakizimana but their chances were squandered.
The hosts, Rayon, came close to opening the scoring after ten minutes following a defensive howler from Herve Rugwiro, but Uliwengu’s effort went wide.
The Blues continued to cause trouble to APR back-line that comprised Rugwiro, Michel Rusheshangoga and Prince Buregeya, but Ulimwengu and Sarpong struggled to find the back of Yves Kimenyi’s net to ensure that the first-half ended goalless.
Five minutes into the second-half, APR made their first change with Innocent Nshuti coming on for Lague Byiringiro to boost their attack, but the new input caused little trouble to a steady Rayon defence that was led by skipper Thierry Manzi and his centre-back partner Ange Mutsinzi.
Both sides kept the chase on for a crucial opener, with Rayon relatively controlling the possession, but it was not until the 92nd minute that Sarpong would score the only goal on the night.
After the league’s biggest fixture between the two local heavy weights, APR host Bugesera FC in their next game, on match-day 24, at Kigali Stadium on April 27 while Rayon will be up against AS Muhanga at Muhanga Stadium the next day.