Second-placed Sydney hosts fifth-placed Adelaide at the SCG tonight, first bounce 7.40pm AEST, with a top-four place resting on the result three rounds out from finals.

The ladder maths is tight. Adelaide sits on 44 points at 11-6, level with Brisbane and Melbourne and separated only by percentage, 0.2 per cent outside the top four after Thursday night's opening game of Round 19. Win, and the Crows almost certainly climb into the four. Sydney, at 13-4 with a percentage of 131.2, is playing to protect the double chance that comes with the top two.

The Swans have made four changes after their 38-point loss to Fremantle in Perth last round. Braeden Campbell plays his first AFL game of the season after a pre-season stress fracture in his shin, Logan McDonald returns from a quad strain, and Riley Bice and Malcolm Rosas Jnr come in, with Joel Hamling, Tom Hanily, Harry Kyle and Caiden Cleary all omitted.

Braeden will play. It's a great story for the footy club," Swans coach Dean Cox said on Thursday. "He played 90 minutes last week, looked really sharp. He's as strong as he's ever been, so hopefully he can show that.

Adelaide regains Isaac Cumming from a hamstring injury through the SANFL, and recalls Hugo Hall-Kahan. Rory Laird misses with an ankle injury and Taylor Walker has been managed after the short turnaround. The Crows arrive with four wins from their past five; Sydney has dropped two of its past five, both to top-four sides.

Round 19 opened on Thursday with Geelong beating St Kilda by 27 points at GMHBA Stadium, 15.12 (102) to 11.9 (75), in front of 23,737. The win came at a price: Max Holmes limped off unable to put weight on an injured ankle and Shaun Mannagh finished with hamstring tightness, per the AFL's match report.

Tonight's game is live on 7mate, 7plus, Kayo and Fox Footy from 7.30pm. Saturday brings four more, headed by Port Adelaide against ladder-leading Fremantle at Adelaide Oval and Collingwood against Carlton at the MCG. By Sunday night, the shape of September will be a good deal clearer, and it starts with whether Adelaide can take a top-four spot out of Sydney's home ground tonight.