Smallwood and his rink of Clint Ireland, Scott Odian and Wade Scoffin jumped out to a 4-0 lead after two ends and cruised the rest of the way.
Casey and his team of Robbie Doherty, Anson Carmody and Josh Barry got one back in the third end, but Smallwood scored a point in each of the next four to wrap up the victory in seven ends.
Smallwood, Casey and Nova Scotia's Glen MacLeod are taking part in a three-team qualifier with the final spot in the Canadian men's curling championship on the line.
MacLeod will face Smallwood and Casey on Friday. The pre-qualifying final is on Saturday with the winner joining the 12-team field for the national tournament.