Ben McClurg sprang a surprise at the Clubworld Travel Ulster junior championship at the Boat Club when he defeated the second seed Matthew O'Boyle in the U-16 event.
McClurg, who is unseeded, set up a meeting with his Windsor club-mate Jakob Robb after a hard fought 6-3, 7-5 victory
Robb overcame Tipperary visitor Evan Whitty-Fitzgerald 6-3, 6-4 while the other semi today will be contested by Matthew Robinson and Ronan McKeever.
It turned out to be a good day for the McClurg family as Ben's older brother, who is seeded to win the U-18 event, also made it into the last four.
He defeated Hilden's Peter Corrie 6-2, 6-4 and will now face Dundalk player Neil Jones.
In the U-16 girls' event top seed Rachel Collins from Naas opened her account with a 6-4, 6-1 victory over Arianna Kennedy to earn a date with Bangor's Amy Rothwell.
Results: boys: U-14: Jacob Fleming bt Juan Quiros 6-1, 3-6, 6-1; Harry Ellesmere bt Rory Cunningham 6-2, 6-1; Kyran Maguire bt Evan Whitty-Fitzgerald 6-3, 6-3; Jordan McKeown bt Caleb Ralston 6-1, 6-2. U-16: Ben McClurg bt Matthew O'Boyle 6-3, 7-5; Jakob Robb bt Evan Whitty-Fitzgerald 6-3, 6-4; Ronan McKeever bt Jordan McKeown 6-3, 3-6, 6-2. U-18: Matthew McClurg bt Peter Corrie 6-3, 6-4; Neil Jones bt David Weir 7-6, 3-6, 7-6; Noah Fleming bt Ardghal McMahon 6-3, 6-4; Alasdair Knox bt Ben Cree 6-4, 6-7, 7-5.
Girls: U-14: Lily Mai McKane bt Jemma Bryson 6-0, 6-0; Caoimhe Smith bt Eimear Smyth 6-2, 4-6, 6-2. U-16 Rachael Collins bt Arianna Kennedy 6-4, 6-1; Amy Rothwell bt Roisin Kelly 6-0, 6-0; Laura Griffin bt Sarah Cousins 7-5, 7-5. U-18 Ruth Copas bt Laura Reid 6-0, 6-3; Aisling O'Riordan bt Aobhinn Kelly 6-1, 6-0; Annie McCullough bt Emily Beatty 6-1, 6-2; Lucy Octave bt Caitlin McCullough 7-6, 7-5.