Defending champion Arouba went down to former winner Al Nahda at the Sur Sports Complex on Thursday night, Mohammed al Siyabi scoring the decisive goal in the 77th minute.
On Friday, hosts Salalah rode a brace from former Oman international Hashim Saleh to edge past Fanja 3-2 in a five-goal thriller. Mohammed al Mussalami put Fanja ahead in the 21st minute and striker Imad al Hosni made it 2-0 by the half-hour mark.
However, Saleh struck twice in a space of ten minutes (33rd and 43rd) to draw level. Ali Bait Said got the winner for the hosts in the 53rd minute. After 21 rounds, Arouba stays on top with 39 points and is followed by Fanja with 38.
Suwaiq is third with 38 and Dhofar is fourth with 31 after the teams played out a goalless draw on Friday. Other results (21st round): Sur 0 Muscat 0, Sohar 0 Al Nasr 0, Al Mussanah 1 Saham 3, Al Shabab 1 Al Khabourah 1.