Neither of the top two were particularly convincing, though, against the bottom two - a cool Jacob Bergstrom finish with 25 minutes to play was all Mjallby needed to beat Oster 1-0 away from home in a match that was littered with near misses at either end.
That was enough to keep the Hallevik side a point clear of Hammarby, who needed an injury-time winner to secure a 1-0 success of their own against last-placed Varnamo, who had Rufai Mohammed dismissed after 19 minutes.
The home side finally made the man advantage count in the 91st minute, when Moise Kabore climbed highest to head home an Abdelrahman Boudah cross.
While 1-0 wins were the order of the day for the top two, 2-0 losses were handed out to the sides in third and fourth.
AIK were shocked on the road against Halmstad, who pulled themselves clear of the relegation zone with two goals in a nine-minute spell in the first half.
Pawel Chrupalla broke the deadlock on 20 minutes, before Naeem Mohammed added the second to give Halmstad a second win in their last three, and condemn AIK to a second loss in their last three.
Also celebrating a 2-0 victory were Hacken, their first win in four matches, as they downed Elfsborg. Two goals from John Dembe did the damage - the first arriving after 33 minutes, then he wrapped up the win in second-half stoppage time.
Elfsborg are now winless in three and three points behind AIK, but remain in fourth thanks to a 0-0 stalemate between the sides in fifth and sixth - Malmo and GAIS.
It's a second draw in succession for the champions, although the previous one was against Mjallby, while GAIS fine form continues; they are unbeaten in their last seven.
Surprisingly, the goals were flying in for Djurgarden, who have only scored 14 goals in 14 games this season, including the five they racked up in a 5-1 trouncing of Degerfors.
August Priske looked to be the man of the hour with two goals in the opening 24 minutes, yet he was outshone by Tokmac Nguen, who scored either side of the break before completing his hattrick from the penalty spot, two minutes from time.
Marcus Rafferty had briefly given Degerfors hope early in the second half to make it 3-1, but that turned out to be a mere consolation as they fall to a fifth defeat in a row, while Djurgarden stay eighth.
The Iron Stoves failed to climb as Goteborg got the better of Sirius, 3-1, despite falling behind to an early Leo Walta penalty.
Max Fenger responded with a spot-kick of his own before the break, then he completed the turnaround three minutes from time and Sebastian Clemmensen sealed the win in added time.
On Monday night, a Daleho Irandust goal in the 88th minute was enough for Brommapojkarna to win 1-0 away from home against Norrkoping, lifting BP up to 10th and above their opponents.