The Eagles won the toss and elected to take first-use of the Numurkah Showgrounds pitch, but quickly fell to 3-21 as the Blues went to work with ball in hand.
Andrew Riordan (56) joined forces with Jedd Wright (25) at the crease to steady the ship though and solid contributions throughout the batting line-up — including 22 from Hadleigh Sirett — steered the visitors to a competitive 146 all-out.
Spinners Liam Gledhill (3-17) and Michael Eckard (3-35) found the most reward for the Blues, with Matt Cline, Tim Braybon and Shaun Downie all chipping in with one wicket apiece.
Downie was the man of the moment in the chase for the home side, hitting 67 at the top of the order to do the bulk of the scoring for his side.
Dylan Grandell (21), Josh Smith (19 not out) and Eckard (14) were able to also get starts against the powerful Katandra bowling attack and despite losing regular wickets the Blues secured victory in the 42nd over of their potential 45.
Luke Patel (2-28) and Ryleigh Shannon (2-33) claimed a pair of victims apiece for the Eagles.
The sides will meet again on February 9 for the one-day final, while Numurkah now has a six-point and handy percentage gap over the Eagles in top spot on the table.
THE GAME
Katandra 146 (Andrew Riordan 56, Jedd Wright 25, Liam Gledhill 3-17, Michael Eckard 3-35) lost to Numurkah 6-147 (Shaun Downie 67, Dylan Grandell 21, Luke Patel 2-28, Ryleigh Shannon 2-33).
STAR PLAYER
Shaun Downie (Numurkah): Downie anchored the chase for Numurkah with 67 at the top of the order after snaring a wicket in the first innings. Will be disappointed he could not see the entire total reeled in, but left the middle order with little to do when he departed with the score 4-125.