Alhambra-Union's slim semifinal prospects slipped away with a 31-13 loss to Harbour.
Kaikorai incurred its first loss since round six, 22-18 to University. But it picked up a crucial bonus point which sealed its spot in the top four.
Zingari-Richmond got off the bottom of the points table with a 20-6 win against Taieri. Dunedin had the bye but has qualified for the playoffs.
Harbour: 31
Alhambra-Union: 13
Alhambra-Union retained a slim chance of slipping into the playoffs but its prospects got lost in the mud at Watson Park.
Harbour second five-eighth Jerome Harimate helped bury its hopes with a three-try haul in the 31-13 win.
The elusive midfield back scored in the opening minute when first five-eighth Logan Allen cantered through a gaping hole and flicked the ball inside to Harimate.
His second try came after a long build-up. The Hawks forwards battered the Alhambra defence into submision and he was able to slip over in the left corner.
The hat-trick came in the dying moments of the match when he danced his way to the tryline following a set piece.
Aside from the opening 10 minutes, Alhambra was competitive. It rallied through a nice try to winger Adam Simpson and trailed 17-10 at the break.
Zach Porter drilled a penalty to close the gap further but the turning point came when halfback Vinnie Isherwood stepped his marker at the ruck and ran 20m to score.
Hawks blindside flanker Ben Whale carried the ball well, hit the rucks hard and was solid in the lineout. Lock Sione Misioli and hooker Sekonaia Pole did not shirk any work, either.
Allen made some nice clearances while fullback Sala Halaleva proved a safe pair of hands in trying conditions.
Hooker Tom Frood had a strong game for Alhambra. Openside Jacob Coghlan covered a lot of territory and Simpson was dangerous whenever the ball reached the left winger.
Zingari-Richmond: 20
Taieri: 6
Zingari-Richmond mastered demanding conditions to record a 20-6 victory over Taieri at Montecillo.
The score on Saturday could well have been far greater had Zingari-Richmond not been plagued by a high error rate in the first half. But its players regrouped and the forward pack laid a platform in the second spell enabling it to dominate territory and possession, forcing Taieri to create play with relatively little ball.
Captain Tom Rowe hot-wired a rampant tight five that created space and opportunity, with fellow lock Matt McCormick and the front row trio of Liam Sharples, Karl Still and Chris Preddy instrumental in cover play and at the breakdown.
Blindside flanker Eli Tonga was a force at the lineout. His ability to win clean ball led to openside flanker Chris Bell taking the pass to crash over for Zingari-Richmond's first try. Bell's speed to the loose ball throughout created opportunity and space for support players.
Second five-eighth Dwayne Corcoran, playing his penultimate game for the side before returning to Ireland, proved menacing with his ability to break the line, while fullback Ciaran Gaffney and wing Chris McNoe were dangerous on the counter-attack, one of which led to the try by Rowe.
Taieri was well-served by centre Christian Kelly who proved a threat in mid-field, and flanker Nick Henderson, while halfback Kurt Hammer cleared the ball well under pressure.
Southern: 45
Green Island: 12
Aggressive play by locks Axel Hohneck and Andrew Sanders helped Southern to a seven-try win over Green Island at Hancock Park.
They controlled the lineout with the help of flanker Adam Knight and made ground with driving runs up the centre.
They were helped by prop Cameron Keech in a powerhouse Southern pack that pushed Green Island back in the scrums.
Southern unleashed attacks from all parts of the paddock and scored six tries with its blitzkrieg rugby and led 38-7 at the break.
It was a complete display by a Southern team, forwards and backs, that used the direct route to the goal line.
The backs were efficiently directed by halfback Josh Walden and they were prepared to attack from all parts of the paddock and were most dangerous when attacking from their own 22m.
Wing Rema Smith displayed exceptional speed as he attacked down the right flank, and fullback Mackenzie Haugh and centre Paul Tupai kept looking for opportunities to counter-attack.
Green Island tightened its defence in the second spell and the game lost its shape as Southern went off the boil.
Lock Jared Williams, the best Green Island forward, had a strong all-round game and Matt McCutcheon was a hard-working flanker. Wing Alex Barnsley ran with determination.
University: 22
Kaikorai: 18
All the rugby in this game was played in a 30-minute period - the first 20 minutes of the first half and the last 10 minutes of the second half. The rest was a rather drab, mistake-ridden forward battle played out in the middle of the park.
Varsity started the game with a point to prove and scored two sparkling converted tries to lead by 14 points inside the first 20 minutes. In the first, from a scrum close the Kaik line, the ball was spun wide then a deft in-pass made to blindside winger Gavin Stark who burst through the tackle and went over.
The second was a long range-effort when centre Josh Timu was fed the ball on the blindside and broke a tackle and scampered 60m to score.
Kaik finally exerted some control and pressure up front, and prop Jonah Aiona scored his obligatory try from a forward drive to cut the deficit. The two first fives, Dominic Clapcott for Varsity and Angus Gray for Kaik, traded penalties to give Varsity a seven-point lead at the break.
The game went nowhere for the next 30 mins apart from another Gray penalty.
Kaik finally strung some solid forward play together and spent a prolonged period in the Varsity 22. The defence was breached and replacement lock Pita Sinamoni crashed over for what looked like the matchwinner and Kaik led by one.
Varsity was not done, however, and stormed back into the Kaik 22. It was winger Gavin Stark who popped up on the other wing and squeezed over in the corner and Varsity put the first ''w'' on the board for seven weeks, much to the jubilation of its supporters.
Varsity was the more enterprising side and was well led by halfback Dylan Monopoli and Clapcott. Stark and Timu were dangerous out wide. The props, Callum Hardie and Angus Williams, were powerful up front in a young Varsity pack.
Kaik's back play lacked imagination and was hesitant and stilted, athough fullback Sean Conner looked assured at the back and his kicking game was sound. Up front, flankers Slade McDowell and Iakopo Petelo Mapu were lively round the track and Blair Tweed was a constant source of lineout possession. Kaik will need to lift to be a threat come semifinals time.