Last year's first-division league winner, Rustaq, was playing in the fifth round of the OPL, and in the past four games, had played out two draws and suffered two defeats.
The victory helped Rustaq climb to tenth spot in the 14-team standings with five points. Speaking after the historic win in the top-flight league, Rustaq coach Mustafa Suwaib said, “I am happy with my boys' performance. I have lot of faith in the team and the players have the potential to achieve much more in the season.”
Suwaib was the architect of Rustaq's terrific run last season and led the team to the first-division title. He was adjudged the best coach of the division at the OFA annual awards earlier this year.
Also on Saturday, former champion Al Arouba scraped to a 3-2 win over Sohar at the Sur Sports Complex to remain among the top three teams with 11 points.
Nine-time champion Dhofar, which played out a goalless draw against traditional rival and five-time winner Al Nasr in a Salalah derby on Friday, leads the standings with 11 points, courtesy its better goal-difference over second-placed Al Shabab.
Shabab was in dominant form as it trounced Jalan 4-1 in Sur on Saturday.
The defeat to Arouba pushed Sohar from second to fourth place with ten points, while Al Nasr is fifth on the leaderboard with nine points.
Defending champion and nine-time winner Fanja, which was held to a 2-2 draw by Al Nahda at the Seeb Sports Stadium on Friday, was trailing in seventh place with seven points.
Oman recorded a convincing 3-0 win over Al Khabourah on Friday to edge Fanja and take the sixth spot on better goal-difference. Former champion Al Suwaiq defeated Saham 2-0 in a Batinah derby on Friday to record its first win of the season. The sixth-round matches are scheduled for Tuesday and Wednesday.
Standings after five rounds: 1 Dhofar (11 pts), 2 Al Shabab (11), 3 Al Arouba (11), 4 Sohar (10), 5 Al Nasr (9), 6 Oman (7), 7 Fanja (7), 8 Al Nahda (6), 9 Al Khabourah (6), 10 Al Rustaq (5), 11 Saham (5), 12 Al Suwaiq (4), 13 Muscat (1), 14 Jalan (1).