Westbury star Jono Chapman claimed the ridiculous figures of 8-16 as his side wrapped up first innings points on the first day of a clash with Riverside.
Three weeks after scoring his maiden Cricket North ton, Chapman secured career-best figures and even took a catch in the field as the Blues were rolled for 102.
The Shamrocks then made their way to 3-128 at stumps to set up a good chance for an outright win next Saturday.
Chapman dismissed Josh Partridge, James Simpson and Tom Garwood in each of his first three overs and when Richard Howe ran out Ben Simpson the Blues were 4-5.
Alex Saunders (16) and Matt Owens (20) faced more than 100 balls each to take Riverside to 4-61 but Chapman's return signalled the end of the resistance.
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Howe was impressed but not surprised by his strike bowler's output.
"He's had a pretty handy couple of weeks that's for sure," Howe said.
"He bowled really well, he took the first three wickets early and probably could have had a couple more.
"We brought him back a bit later when we hadn't made any inroads into Riverside's batting line-up and he took another five so it was fantastic, not only for himself but also for us to keep us going."
Riverside removed Will Donald early and later snared Ollie Wood and Dane Anderson in the space of three balls thanks to an Emma Manix-Geeves stumping and a Garwood caught-and-bowled.
But promoted pair Daniel Murfet (57 not out) and Corey Briggs (25 not out) put on an unbeaten 76 to end the day.
"We'll assess now and see what happens, we'll try and give ourselves the opportunity to win outright next week but we'll just have to wait and see," Howe said.
"If the wicket's like it was today we'll have a look at bowling again, but otherwise we'll try and score a few more runs."
- Daniel Murfet 57*
- Corey Briggs 25*
- Lyndon Stubbs 24
- Jono Chapman 8-16
- Luke Midson 1-6