Anthony McGill beat veteran Jimmy White 4-1 in their quarter final, to set up a tie with Ireland's Ken Doherty.
Doherty had earlier secured a 4-2 win over China's Zhang Anda.
Andrew Higginson beat Mark Davis 4-3, and will meet Stephen Maguire, who beat Jack Lisowski in a 4-1 whitewash.
Riga Masters
Day defeats Maguire for Riga Masters victory
25/06/2017 AT 20:44
On the other side of the draw, Joe Perry's 4-1 win over Paul Davison means that he will meet Ryan Day, who defeated Kyren Wilson 4-3.
Mark Williams, who beat Robbie Williams 4-2, will take on Mark Joyce after he beat Sam Bird by the same scoreline.
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