West Augusta took the premiership points in their season defining win over South.
The reigning premiers began life without captain Greg Shirley with a disappointing loss that allowed Quorn to close in on them on the ladder.
West produced a terrific team effort as the Hawks chased down South's target of 136 with four wickets in hand.
South openers, Corey Cuffe and Rowan Irvine began the afternoon well, negotiating the first ten overs with few issues.
The stand was then ended with Irvine run out for eight but Will Waterworth picked up where he left off.
The in-form number three was full of confidence and, along with Cuffe, put South in a good position before the opener was dismissed for 26 by Steven Hutchins.
Todd Kernahan returned to the side in Greg Shirley's usual number four position and looked determined to step up.
The runs were coming slowly but with wickets in hand, South were still on top.
Kernahan fell to Josh Dunstan for 15 before the left arm spinner lifted his side with the dismissal of Waterworth just as he started to accelerate.
His brother, Rex, replaced him with just nine over remaining and only 108 on the board.
Marcus Gill looked to increase the total to something defendable and made his way to 16 before Jason McInerney sent him back.
After that, McInerney (3/5) and Foote (2/18) continued to cause issues for the South batsmen in an important ten over period.
South's total was salvaged by Aaron Vater and Marcus Kerin who scored 20 crucial runs in their ninth-wicket stand to help their side get to 9/135.
West began their run chase with a point to prove after two poor batting performances against South this season, but they didn't have a promising start as Chris Shiel fell for just two.
Ashley Stroyan and Lachlan Hollitt got things going for West in a terrific partnership that turned the game right in their favour.
The pair were scoring at a good rate in the first fifteen overs before Trewartha broke through when he castled Stroyan for 37.
Despite seeing the end of Hollitt, West kept on top as Mitchell Foote and Rhys Dadleh refused to give South a chance to take quick wickets while keeping the scoring rate up.
Foote fell for 19, but his side were in a commanding position and after he was out, Dadleh, Dunstan and Lachie Woodforde scored the final 24 runs needed for victory.
South's attack didn't seem to trouble the West batsmen but Aaron Vater was the pick of the bunch with 3/39.
West were far too good in the end for South who will look to pick themselves up when they meet the bottom ranked Central/Stirling side while West will face Quorn in an important clash as the two sides continue their battle for second position.
Quorn vs. Central/Stirling
Quorn completed a confidence-building win over Central/Stirling to close in on South in top position.
After losing their first four wickets for just 30 runs, Scott Williams and Corey Finlay re-built the innings and got their side all but over the line in a 61-run stand.
Central started in just about the worst way possible when opening batsman, Lucas Hill, was run out in the second over with the side still yet to score.
This brought Tyson Bray to the crease for his one and only game for the Tigers this season.
He and Connor Harrison complemented each other well but their partnership was short lived as Harrison picked the wrong length to pull of Cameron Finlay and was bowled for 16.
Soon after, Bray was dismissed for 15 when a diving catch from Matt Griffiths handed Corey Finlay his first wicket.
Nathan Khan and Dean Miller steadied the ship and made it through to the first drinks break but had a big job to do upon the resumption.
Khan was looking particularly good in the middle, pouncing on anything in his hitting zone, but Corey Finlay struck again to dismiss his partner for 12.
Skipper Toby Baxter's stay at the crease was short as he became Finlay's third victim and Central stumbled to 5/80.
Quorn then took the game by the scruff of the neck and after getting the breakthrough wicket of Khan for 39, cleaned up the tail with ease.
Tom Finlay came back into the attack and took two late wickets, but his spell was ended prematurely when his second above-waist-high no ball saw him out of the attack.
It didn't matter though as Mark Francis picked up the last two wickets to bowl Central out for 101.
Quorn were certainly the favourites heading into their run chase but Dean Miller and Will Tucker combined for an outstanding opening partnership with the ball.
Tucker reaped the rewards with the early wickets that Central desperately needed.
He claimed both openers, Tom Finlay and Kade Baker as well as Matt Griffiths within his first four overs while Miller kept the pressure on with plenty of dot balls.
At 3/17, Alex Hosking looked to calm his side down and started to get going, but Tucker struck again with the massive wicket of the Quorn skipper.
A lot then rested on Scott Williams and Corey Finlay to trim the target down and they got off to a good start without being troubled.
The two veterans put on a stand that ultimately won Quorn the game as each run put more pressure on the Central bowlers.
They got Quorn to within 11 runs of victory and it took a spectacular diving catch for Nathan Khan off his own bowling to get the breakthrough.
After Williams departed, Finlay was then run out to keep the door slightly ajar for Central, but it was quickly slammed shut as Mark Francis and Rob Britza guided Quorn home by four wickets.
Williams finished as the top scorer with 43 while Finlay's 23 was just as important.