The 19-year-old midfielder was let go by the Trotters over the summer, having also been on loan at Hamilton early in 2012. He barely appeared during his time at New Douglas Park, although he has been capped by Scotland at a number of age groups.
MacGregor has been training with the Buddies for a fortnight and has now signed until the summer. There's no indication yet as to whether he's been brought in for the first team or one of the youth sides.
Story source: The Official St. Mirren Website
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