Salgaocar, who had lion's share of exchanges and ball possession, scored the winner through Sobrosa in the 57th minute to take their tally to 27 points from 23 matches.
Prayag United, who failed to create an impact upfront in the absence of their suspended key striker Ranti Martins, remain on 35 points from 22 matches.
The Goan outfit could have increased the lead in the later part of the second half but timely save from visitors' keeper Sangram Mukherjee thwarted their efforts.
Being relatively a new surface for both teams, they tried to guage each other's strength. Salgaocar, who made early advancement into the rival's half, had the first chance to surge ahead but Josimar Da Silva shot out the ball.
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Randeep Singh, who controlled the midfield, kept the attack moving along with Francis Fernandes. Fernandes, who worked his way well on left flank, had two chances midway in the first half to put his team ahead but his first attempt went off the target and the later could not beat the keeper.
Salgaocar came close to scoring in dying minutes of the first half when an attempted volley from Milagres Gonsalves off Anthony D'Souza cross was tipped over by keeper.
The local team continued their attack in the second half too and finally broke the deadlock in the 57th minute when defender Sabrosa tapped the ball into the net off Randeep Singh free kick to give Salgaocar full points.