The bottom team Halmstad needs points regardless of the opponent, but initially, it didn't seem like there was a 22-point difference between the teams before the meeting at Tele2 Arena in Stockholm.
The Halländers had three sharp chances for a leading goal, but Hammarby goalkeeper Warner Hahn made three cannon saves during the goalless first half.
"Not good at all"
It's not good at all. We're giving away too many chances and it's our mistakes, says Hammarby midfielder Tesfaldet Tekie to Max during the break.
Center back Ibrahima Fofana had a tough day and Hammarby coach Kim Hellberg chose to replace the Guinean with Pavle Vagic when the second half kicked off.
It got better with Hammarby eyes after the break, and in the 53rd minute, the winning goal fell. Josef Erabi failed with a shot, but it turned into a perfect pass to Bazoumana Touré, who scored 1-0 behind Tim Rönning in the away goal.
Hammarby took over strongly after the leading goal and had two balls in the goal frame, but no more goals fell.
The win means that "Bajen" is the new second-placed team on 47 points, but with one more match played than Djurgården (46 points) and AIK (45). Malmö FF leads the Allsvenskan on 56 points and can, in practice, only be caught by Hammarby in the battle for the championship title with a win against Värnamo on Sunday.
For AIK and Djurgården, home matches against Häcken and Kalmar await on Sunday.
Tough loss for Västerås
For Halmstad (24 points), the loss means that the team remains on the qualifying spot, but behind, Kalmar (22 points) and Västerås (19) are chasing.
Västerås was on its way to a point away against mid-table team Mjällby, but in the 88th minute, Tom Pettersson decided for the home team with his 2-1 goal.
After the weekend's matches, four rounds of the Allsvenskan remain.
Corrected version: Previously, the wrong opponent for Malmö FF in Sunday's match was stated.