Muir hit 43 at the top of the order and was the last man out with the score at 109 after 43 overs in the middle.
He faced 84 deliveries and hit two fours as fellow opener Sam O'Brien was the next-best scorer with 13.
Rory Duffy and Ethan Beck were the two stifling influences with ball in hand, Beck taking 1-12 from his six overs and Duffy a remarkable 4-15 bowling in tandem with the new ball, while Sam Holland went for just seven off four overs.
Meanwhile, Euroa was humming along in its run chase, with Walter Jackson unbeaten on 19 and Zach Burton yet to score.
The Magpies are 3-58 from 20 overs chasing Numurkah's 75.
Numurkah only had 10 batters and lasted 25 overs in the middle as Cale Robertson (3-10) and Kusuma Wolfenden (2-11) turned the screws.
Kyren Dawson top-scored for Numurkah, making a 50-ball 27 with five fours, but he was the only batter to pass 10 for the side.
Mooroopna had the bye in A-grade.
In B-grade, Bayden Hutchins and Jake Davidson scored 40s for Northerners as the side set Notre Dame-St Brendan's 218 to win.
Hutchins and Davidson came together at 2-1 and, while the two retired on 42 and 40 respectively, it was 100 runs before Northerners lost another wicket, while Zavier Davidson also made an unbeaten 43.
The side only lost six wickets with Adam Welk taking three of them, finishing with 3-18 from four overs.
Will Trower led the way with 40 retired for Waaia as the side put together 4-171 against Tatura, while Pine Lodge-Karramomus could only manage 84 from 44.4 overs against Mooroopna.
Nagambie's juniors put on 4-196 with Blake Ezard (42), Garry Bhour (43) and Angus Nash (39) all retiring unbeaten as part of a 45-over score of 4-196.
Ben O'Brien was the pick of the bowlers with 2-17 from seven overs for Old Students.
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