Port Adelaide has pulled off a brilliant against-the-odds win over St Kilda by seven points at Marvel Stadium.

A career-best showing from former No.1 pick Jason Horne-Francis and an influential hand from Jeremy Finlayson were instrumental in the win, with the latter taking two crucial marks in the dying minutes as the spare in defence to seal the 12.11 (83) to 11.10 (76) victory at Marvel Stadium.

The lead changed hands four times in the second half as neither side could shake off the other, with fierce tackling (and a subsequent lack of composure) a feature.

St Kilda had shown just why it was sitting pretty in top spot in the first quarter, playing with positivity and finding a variety of paths to goal, with its defence standing firm and Rowan Marshall directing play around the ground.

The Power didn't drop their heads despite an 18-point deficit at quarter-time, improving in their contested-ball wins and increasing their tackle pressure to kick four straight goals, taking the lead for the first time at the 17-minute mark of the second quarter.

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Port Adelaide struggled to make a meaningful impact in attack in the first quarter, almost sleepy in setting up its forward structure, but it worked its way back into the game beautifully. 

The second-term woes of the Saints were starkly demonstrated in the stats, recording just four behinds from 16 inside-50s, while the visitors were impressively efficient with 4.5 from 10 entries.

Horne-Francis was Port Adelaide's most dynamic midfielder even when the team was struggling in the first quarter, the second-year bull providing some much-needed speed around the stoppages. He faded somewhat in the second half, but recorded a career-high 10 clearances to half-time (11 for the game) and finished with 25 disposals and seven tackles.

Jack Sinclair (33) worked hard off the half-back flank all match, Jack Steele (28 and nine tackles) tried desperately to drag the Saints over the line and Marshall (28 hitouts, 26 disposals) was imperious in the ruck against the young Brynn Teakle. 

Xavier Duursma clashed knees with Marshall halfway through the first term, and struggled to get any speed up when he returned to the field following treatment. He was subbed at the first break.

Nasiah Wanganeen-Milera was crunched in a teal sandwich late in the second and the in-form Cal Wilkie needed his right ankle re-strapped in the third, but both played out the game.

ST KILDA  5.2  5.6  8.8  11.10 (76)
PORT ADELAIDE  2.2  6.7  9.10  12.11 (83)

GOALS
St Kilda:
 Owens 2, Gresham 2, Higgins, Cordy, Membrey, Wood, Butler, Steele, Clark
Port Adelaide: Rioli 2, Powell-Pepper 2, Dixon 2, Finlayson 2, Duursma, Boak, Houston, McEntee

BEST
St Kilda: Steele, Sinclair, Marshall, Wanganeen-Milera, Wilkie
Port Adelaide: Horne-Francis, Boak, Butters, Houston, Powell-Pepper

INJURIES
St Kilda: Nil
Port Adelaide: Duursma (left knee)

SUBSTITUTES
St Kilda: Marcus Windhager (replaced Cordy in the third quarter)
Port Adelaide: Riley Bonner (replaced Duursma at quarter-time)

Crowd: 25,845 at Marvel Stadium