Western United was denied a perfect record heading into the Far West football A grade finals as a fourth-quarter comeback saw it share the points with Koonibba on Saturday.
In difficult conditions the Tigers looked to have pulled away at the final break, only for Koonibba to come roaring back for an 8-8 (56) to 8-8 (56) draw.
Things looked to be going to the script in the first term as Western United kicked four goals to one to lead by 22 points at quarter-time, yet Koonibba hit back with three goals in the second term to reduce the deficit to eight points.
Westies kicked the only two goals of the third quarter and after 11 straight victories could sense another was on the way as they led by 18 points at three-quarter time.
Yet the Roosters showed determination in the final quarter and used the conditions to their advantage to ensure a thrilling finale.
They kicked four goals to Western United's one, with the teams locked at the final siren.
Jarden Stoetzer kicked five goals for the Tigers, while Jesse Lennon, Royden Miller and Maliki O'Loughlin grabbed two apiece for Koonibba.
The Blues made it three wins out of four to close the regular season after a big second half helped them to down Thevenard by 32 points.
They trailed at half-time but then dominated with eight goals to three to win 15-12 (102) to 11-4 (70).
Thomas Clayton of the Blues and Thevenard's Dom Denton enjoyed their own personal duel as both kicked six goals, with Andrew Cox and Trevor Peel adding three each for the Blues.
It was a day to celebrate for the Blues as they commemorated 30 years since the amalgamation between the Ceduna and Smoky Bay clubs, wearing a replica of the original guernsey with all premiership players' names printed on the jumper.
The Blues got the jump with the opening two goals which helped them to a 10-point lead at quarter-time.
They also opened the second term with two majors only for Thevenard to hit back with six of the next seven goals to lead by three points at half-time.
The Blues dominated the third quarter as they kicked five goals to one behind - including three for Clayton - to hold a commanding 30-point lead.
Thevenard needed a good start to the final term to have any hopes of a comeback yet it was the Blues who grabbed the opening two goals to effectively end the contest, before Denton kicked his final three.
The teams will meet again at Thevenard in this Saturday's first semi-final, with the loser to be eliminated.
In the B grade, Koonibba completed a clean sweep with an 81-point triumph over Western United.
The Roosters dominated throughout to win 17-12 (114) to 5-3 (33).
The hosts led by 24 points by half-time and restricted the Tigers to just one more goal while booting four in the third term and finishing strongly with six goals.
Koonibba shared the goals around, led by Gareth Dudley's four and three for Edwin Gray and Derek Gray.
Thevenard came away with an 8-11 (59) to 3-4 (22) win against the Blues.
Toby Lee kicked four goals as the Magpies prepared for the finals with a 37-point victory.
The Blues kicked just one goal to half-time as they trailed by 17 points, with the third quarter a tight tussle.
The Magpies controlled the fourth quarter with three goals to three behinds to secure the win.
Thevenard and the Blues will clash once more in the first week of the finals.